Living With, ‘If Only . . .’ : Crime: A knock on the door has forever changed a family’s life. And 9-year-old Laura Arroyo’s father seems almost unable to cope with the grief of his daughter’s death.

In the past three months, Luis Arroyo has asked himself the same question at least one thousand times.

“Why didn’t I go answer the knock at the door that night? Why couldn’t it have been me instead of Laura?”

On June 19, 9-year-old Laura Arroyo was watching television with her mother in an upstairs bedroom when she dashed downstairs to answer a knock at the front door of her family’s San Ysidro condominium.

Arroyo remembers his daughter yelling, “I’ll get it,” as she ran to answer the knock.

It was about 9:10 p.m., and the last time that Laura’s family saw her alive. The child’s parting words still ring inside Arroyo’s head as part of an interminable nightmare.

Incredibly, nobody--including the Arroyos--in the well-tended, normally safe row of condominiums, which are heavily populated with children, heard or saw anything.

When they realized 10 minutes later that Laura was gone, her anxious father and other family members drove around the area, looking for his missing daughter. While some family members searched, others quickly reproduced 300 flyers with Laura’s picture and passed them out in the darkness.

But their efforts proved hopeless.

Two women reporting for work the next morning discovered Laura’s body about 6:30 a.m. The killer or killers had dumped the body on a sidewalk, 5 miles away from the Arroyo home, in front of a bayside industrial complex in Chula Vista.

Police said that Laura, who was still dressed for bed, with bare feet and in her pink night clothes, was bludgeoned about the head and stabbed repeatedly in other parts of her body.

More than three months later, there have been no arrests. However, Chula Vista detectives said last week that they have been sifting through “a fair amount” of leads and forensic evidence, some of which is being analyzed by the FBI crime laboratory in Washington.

Although the investigation has taken a painstaking course, police are confident of solving the case, said Detective Wayne Maxey. Investigators were unwilling to discuss specifics, such as motive, but Maxey said detectives “are keeping close tabs on people we’re interested in.”

Meanwhile, the Arroyo family remains haunted. Arroyo and his wife, who is also named Laura, visit their daughter’s grave three or four times a week, including every Sunday after they attend Mass.

The couple’s two sons, Jaime, 11, and Luis Jr., 10, have struggled to adjust to their sister’s death. Other students at Nicoloff Elementary School, where Laura was a third-grader, still point at the boys and ask them about their sister’s death, Arroyo said.

“Our lives have been changed by this,” said the 32-year-old tow truck company worker. “The boys’ schoolwork has suffered. They are now afraid to play outside and spend most of their time indoors. They’re afraid to answer the door.”

Friends and acquaintances said that Arroyo has been wracked by unimaginable grief over Laura. In a recent interview, tears welled in Arroyo’s eyes as he discussed his daughter’s death.

He has gone through periods when he blamed himself for not doing enough to protect Laura, Arroyo said. His daughter was taken away while he was bathing Jaime and Luis Jr.

If only he had bathed his sons earlier, he would have been able to answer the door. If he had answered the door, Laura would still be alive, Arroyo has told himself over and over. But no matter how many times he questions himself and replays the events of that tragic night, Arroyo comes to the same conclusion:

“All Laura did was answer the door. How many times do people do that every day? It’s one of those things that everyone does instinctively. I mean all she did was answer the door. Why should you expect to find danger in that?”

John Clark, Arroyo’s employer at J.C. Towing in Chula Vista, said the death overwhelmed Arroyo.

“At the beginning, he would go to the cemetery every single day, during his lunch hour and after work,” Clark said. “He would spend four or five hours at Laura’s grave. He still sleeps with his daughter’s picture beside him, and also sleeps in her room. Laura’s room has remained untouched.”

The case took a bizarre twist in July, when thousands of people said they saw Laura’s image on a blank billboard near the corner of Broadway and Main Street in Chula Vista. The apparition was seen only at night, when the billboard was lighted.

Chula Vista police said that up to 30,000 people were coming nightly to view the billboard. Many believers said they saw Laura’s face in the shadows cast by the lights on the white screen.

One night, the owners of the billboard, Martin Outdoor Advertising, turned off the lights. But, several hours later, because of what Martin officials said was a malfunction in a timing device, the lights came on automatically.

Eventually, the company offered to put a giant picture of Laura on the billboard, along with the phone number of a crime tip line opened by Chula Vista police. The huge, high-resolution, computerized image of the girl was accompanied by the words: “In Memory . . . Laura Arroyo” and is still on display.

Some believers left crucifixes and built small shrines under the billboard. Although the crowds have thinned out considerably, a few people still leave flowers and votive candles.

Arroyo still visits the site every day.

“I go there every night to see my daughter. I light the candles that people leave there and talk to Laura. I stand there, pray and talk to Laura,” said Arroyo, struggling to maintain his composure. “I ask her to help us find the person who hurt her. I know that God will allow her to talk to us, if only once, so we can catch the terrible person who hurt her.”

“She was a little girl. How can anybody do something like this to a child? What reason could they have. She wasn’t old enough to hurt anybody.”

Maxey said the small group of Chula Vista homicide detectives have also been moved by the young girl’s death. Maxey talks to the Arroyos at least once a week, offering them encouragement and comfort.

“The whole department has taken an interest in this case,” he said. “It has become a personal issue with the officers here. . . . It’s a case that we don’t want to drop off by the wayside. I talk with the Arroyos quite a bit. I have told them we are confident that we will resolve this case. Justice will prevail, but we have to be patient.”

Both the police and Arroyo are convinced that someone in the community knows the identity of Laura’s killer or killers. In an effort to help police solve the case, the tow truck industry has donated money to a reward fund established by Clark.

The fund totals $5,000, but contributions are still arriving daily from towing businesses across the country, Clark said.

“There’s some scumbag out there who knows something, and we’re hoping this money will make them squeal,” Clark added. “Whoever did this doesn’t know that they’ve destroyed a wonderful family. I mean, you’ve never seen a guy who is more dedicated to his family.”

Laura’s death, which has been reported nationwide, has also moved others. Two weeks ago, a complete stranger from Las Vegas came to offer her sympathy to Arroyo and his family.

“She said that she saw Laura’s picture on the news and something told her to come talk to us. She prayed for Laura and visited the billboard. My daughter has touched many people,” Arroyo said.

Meanwhile, Laura’s face and smile linger on the billboard, looking down on Broadway. Arroyo said he wonders if his daughter’s picture has also looked down on her killer or killers.

“I wonder if she has seen the people who hurt her,” he said. “I also find myself now looking at strangers when I’m driving. I wonder if somewhere I haven’t seen the people who hurt my daughter.”