Luis Donaldo Colosio finished the last speech of his life and descended from the makeshift podium of a pickup truck into the chaos of a campaign rally in a Tijuana shantytown. The crowd pressed around the presidential candidate, jostling his entourage in the sloping dirt plaza.
As the dance tune "The Snake" blared suddenly in the background, a young man in black emerged from the crush, grasped Colosio's arm, placed a .38-caliber revolver against his head and fired.
Panicked aides carried away the mortally wounded Colosio. Bodyguards hustled the captured gunman to another vehicle, but its path was blocked by journalists, city police and citizens. They shouted that the assassin would be killed or disappear--and Mexico would never know the truth.
One year later, an enigmatic, 24-year-old factory worker named Mario Aburto Martinez is serving a 45-year sentence for Colosio's murder.
But otherwise, the instinctive fears expressed by the crowd have been realized: The Colosio assassination remains a mystery. It now embodies the intrigue and uncertainty of an extraordinary, historic moment in Mexico, where politics is coming to resemble a detective story.
By arresting an accused second gunman and alleging a cover-up, authorities have sketched a fascinating but unproven plot.
Emerging evidence strengthens the theory that Colosio fell victim to a political struggle in his own Institutional Revolutionary Party, or PRI, government officials say. The investigation is focusing, at least in part, on hard-line ruling party factions and suspected ties to drug cartels, an official close to the probe said.
"It points to a fight between political groups involving the cartels," the official said. "It is becoming hard to tell which field you are in, politics or drugs. This is a dangerous direction."
An unprecedented development in a separate assassination has heightened suspicions and expectations. Police last month arrested Raul Salinas de Gortari, the older brother of former President Carlos Salinas de Gortari, in the killing of the PRI's No. 2 official. Although the former president has not been implicated in that murder, critics have called for him to tell investigators all he knows about the Colosio assassination and the potential political motives and links behind the two crimes.
"Surely he has a great deal of privileged information," said Sen. Alfredo Ling Altamirano, a member of a legislative panel monitoring the Colosio probe. "It is obvious that he has information about the internal struggle. If we are talking about a political motive, this is a line of investigation. . . . There are power groups, and Carlos Salinas knows who they are and who leads them."
So far, authorities have not made public any hard evidence linking the half a dozen suspects in the Colosio assassination to each other, let alone to a mastermind. The chaos at the crime scene in the neighborhood of Lomas Taurinas has carried over into the investigations.
The latest in a string of official theories is full of ambiguities.
President Ernesto Zedillo is reportedly sure that Colosio was killed as part of a plot, and he will take the investigation as high as necessary, according to officials. But to do that, the special prosecutor, Pablo Chapa Bezanilla--the third prosecutor appointed in a year--has had to practically start over. He is reinterrogating witnesses and re-examining evidence on a trail that is now cold.
"The first phase is the crime scene," said Juan Ignacio Zavala, the attorney general's spokesman. "We are looking at the role that every one of the people around Colosio played. This takes a great deal of time. It would be risky to talk about a (mastermind) at this time."
But the investigation must go beyond street-level suspects to the elite circles where a conspiracy must have originated, critics say.
"They are still in Lomas Taurinas," the neighborhood where the assassination occurred, commented Fernando Gomez Mont, a former Baja California senator who served as a liaison between state and federal police on the Colosio case. "The special prosecutor has done good work. But he is far from completing his work. He must know that."
The hunt for a mastermind has focused on Colosio's own security commanders and, therefore, on the PRI and government.
Othon Cortez Vasquez, 28, the accused second gunman, and Fernando de la Sota--head of a shadowy campaign security unit who is now under arrest for alleged perjury in the case--had ties to Colosio's security chief, Gen. Domiro Garcia Reyes.
That alone, legislators said, makes a compelling case for also investigating Garcia Reyes, who is a member of the Estado Mayor, the military corps that protects Mexican presidents.
De la Sota has served prison time for drug corruption and has his own mysterious ties. Documents show that his security team was financed by the Grupo Toluca, a political faction led by businessman and former government minister Carlos Hank Gonzalez, one the most powerful figures of the PRI's hard-line wing.
Roberto Alcantara Rojas, boss of the Mexican teamsters union affiliated with the group, helped get De la Sota the sensitive campaign post by introducing him to commanders of the presidential guard, documents show.
"What we are demanding is that they go to the top," said legislator Ramon Sosamontes of the Colosio commission. "Roberto Alcantara, who is Mexico's small-time Jimmy Hoffa, organized a security detail made up of delinquents and torturers."
A knowledgeable official said the special prosecutor has been examining Hank's political group, which is based in the state of Mexico, among other leads.
The questions about a general in the presidential guard raise questions about the presidency itself. Numerous politicians and columnists have urged an investigation of Jose Cordoba Montoya, the former presidential chief of staff who was abruptly replaced after the assassination, and of former President Salinas.
The attorney general's office recently denied that Cordoba and Garcia were suspects. Salinas has publicly insisted that he has not interfered with the Colosio investigations in any way; he staged a brief hunger strike to dramatize his position.
Salinas' first special prosecutor, Miguel Montes, told reporters recently that the former president had seemed more concerned about his image than the progress of the case.
When contacted by The Times, Montes declined comment, saying: "I want my successor to benefit from the tranquillity to investigate that I never enjoyed."
Montes, a Supreme Court justice with little investigative experience, has been roundly criticized. His tenure culminated with cries of a cover-up when he discarded his original theory that several people were involved in Colosio's killing and concluded that Aburto had acted alone.
But many Mexicans have focused on a possible PRI role in Colosio's death because of the political tumult that engulfed his candidacy from the very start. His campaign was overshadowed from the outset by the January, 1994, guerrilla uprising in the southern state of Chiapas and an internal party challenge. He was plagued by rumors that he would be replaced.
He also rebuffed overtures from drug lords, according to current and former government officials. Some believe that the conspiracy teamed politicians and cartel allies who saw Colosio as a threat.
The suspected drug link gained prominence this week when Baja officials confirmed to The Times that they are seeking two federal police commanders in the ambush slaying of Tijuana Police Chief Federico Benitez Lopez. He was killed five weeks after Colosio and had clashed with drug traffickers and their protectors in the federal and state police.
State officials, who have been working with the Colosio investigators on the Benitez case, are increasingly convinced that the deaths of the chief and the candidate were related. The chief suspected a cover-up in the Colosio case and was investigating the possibility of a second gunman--now the dominant theory.
A peculiar, seemingly obscure tip has buttressed the theory that the Benitez and Colosio assassinations are linked and that federal officials played a role.
It was offered by a mystery caller in Sonora, whom later investigations showed to be a former secretary of a top official in the federal attorney general's office in Tijuana. The woman, who offered to give names and details, was also linked to the two commanders now accused in Benitez's slaying.
The telephone tip raises some of the nagging questions that have led the special prosecutor into the depths of Mexico's troubled political system.
But even in the public case developed thus far--with its emphasis on evidence drawn from videos and photos--critics say prosecutors have much more to do.
"The great mystery is that there seems to have been more attention on what happened on March 23 and afterward, rather than on what happened before March 23, which is the key," said a former high-ranking law enforcement official.
The two-gunman scenario arose after forensics experts discarded the thesis that Aburto shot Colosio in the right side of the head and the left side of the torso in rapid succession. Concluding that Colosio did not spin around between shots, investigators identified Cortez, the alleged second gunman, as the man standing inches to the left of Colosio at the fatal moment. Videotapes and photographs do not show Cortez's hands before Colosio is shot; when Colosio is sprawled on the ground, Cortez's hands are empty.
But prosecutors based their latest charges largely on recent questioning of three witnesses who had testified last year. According to last month's sworn statements obtained by The Times, Sarah Belen Mackeiz said she saw Cortez pointing a gun toward the candidate; Jorge Romero Romero said he saw a hand press a gun against the candidate's beige jacket.
But only Jorge Amaral, who said he was changing the statement he gave last year, described seeing Cortez fire. He said he heard someone to Colosio's left yell, "Kill him!" He said the fleeing crowd parted, allowing him to see "perfectly the (gun) barrel and the left side of the person who fired."
Still, at least one prominent publication in Tijuana, the influential weekly Zeta, rejects the charges against Cortez, calling the witness accounts late and dubious. And former Sen. Gomez wants more proof.
"I cannot say that I am convinced without a doubt that there were two gunmen," he said. "It is not more than a solid theory."
Meantime, the convicted assassin remains the mystery at the heart of the mystery.
Special prosecutor Chapa visits Aburto in prison regularly, and the two have established a rapport, a government source said.
The tough and articulate Aburto jousted with prosecutors during his trial. Conversely, he has also shown stoicism, receding into a near-trance after his arrest.
"He is an extraordinarily cold and controlled man," the former high-ranking law enforcement official said. "When a man has just killed another man, usually there is an adrenalin rush. But he looked as if he had just returned from a day in the country. He was calmer than we were."
If money or ideology induced Aburto to become the triggerman in an elaborate plot, he must have been extensively recruited and prepared.
But authorities have revealed no persuasive proof that Aburto was in contact with conspirators.
"They have not been able to develop who Aburto was," Gomez said. "They don't know who his friends were. There are a lot of holes."
* WHO BENEFITS? Mexico bailout spurs questions about U.S. aid. D1
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Surrounded by Suspects
Luis Donaldo Colosio is shown moments before being gunned down at a campaign rally in Tijuana a year ago. During subsequent investigation, many of those near Colosio--and believed to be allies--have been accused of plotting to kill him.
1) Luis Donaldo Colosio, presidential candidate of the ruling Institutional Revolutionary Party, shown at a Tijuana campaign rally seconds before he was mortally wounded by two gunshots.
2) Mario Aburto Martinez (his face is partly obscured, his wrist visible as he grabs Colosio's arm just before shooting him in the head.) Aburto, arrested at the scene and later convicted of killing Colosio, is serving a 45-year prison sentence.
3) Tranquilino Sanchez Venegas (wearing cap). A member of a volunteer Tijuana security force, he was later charged with helping the gunman push through the crowd. The special prosecutor later reversed himself, but Sanchez still faces trial on the original charges.
4) Vicente Mayoral Valenzuela. Also an imprisoned member of Grupo Tucan, he is a former Baja homicide detective who was charged along with Sanchez as part of a conspiracy to aid Aburto by pushing aside Colosio's bodyguards.
5) Rodolfo Mayoral Esquer. He is Vicente's son and was charged as part of the original conspiracy theory.
6) Othon Cortez Vasquez. He was arrested late last month as part of a new conspiracy theory, in which he is accused of being the alleged second gunman who fired the shot into Colosio's side. He has worked as a driver, aide and bodyguard to Tijuana political bosses.
7) Domiro Garcia Reyes. A general in the Estado Mayor, the elite military unit that guards Mexican leaders, Garcia was Colosio's security chief. He has become the subject of intense attention because of his ties to Cortez, the alleged second gunman, and to another campaign security commander charged in an alleged cover-up. Garcia has not been charged in the case.