The gunman who shot and killed officers in Baton Rouge was named Gavin Eugene Long, according to a U.S. law enforcement official. Long was a 29-year-old from Kansas City, Mo. Today was his birthday.

A second official described Long as a "black separatist."

"What is almost dream-like about all this," said Terrence Horad, who lived next door to Gavin Eugene Long in Kansas City, Mo., "is that you never know what it could be that would push someone you know, like a neighbor, right over the edge."

"But if bad things keep happening to a certain kind of people — black or white or green — some people just aren't going to take it anymore. They'll think, hey, those are our kids getting shot down," Horad said.

"But we can't take the violent approach or there'll be dead bodies laying all over the place. But I can kind of understand."

The three officers shot and killed by a gunman in Baton Rouge, La., early Sunday were remembered with fondness and sorrow, two veterans and a rookie added to the grim roll of law enforcement officers killed in the line of duty.

“These men are husbands, fathers, sons and brothers,” Sheriff Sid Gautreaux of the East Baton Rouge Sheriff's Office said in a statement.

Just 10 days after five officers were killed in Dallas, the shooting in Baton Rouge marked the fourth high-profile deadly encounter in the nation involving police in the past two weeks. Here’s a look at the officers killed in Louisiana’s capital city. 

Gavin Eugene Long, the ex-Marine who shot six police officers in Baton Rouge, La., on Sunday, killing three, had self-published three books under the name Cosmo Setepenra, which he also used in online forums.

The books are a combination of New Age-style jargon, pseudo-science, motivational bromides, health tips and racial theory. 

"The Cosmo Way: A W(H)olistic Guide for the Total Transformation of Melanated People, Vol. 1: The Detox" claims to help readers "achieve [their] optimal nutritional, physical, emotional and spiritual goals." In the book, Long harshly criticizes Western medicine.

The Washitaw Nation, the sovereign-citizenry group that Gavin Long declared himself a member of, was founded decades ago by a black Louisiana woman named Verdiacee Turner, who called herself Empress Verdiacee “Tiari” Washitaw-Turner Goston El-Bey. Its core tenet is that followers are descendants of the “Ancient Ones,” or “black ones," who occupied the North American continent tens of thousands of years before white Europeans. 

Turner, now deceased, developed an entire mythology around the idea that land sold by France to the United States in 1803 in the Louisiana Purchase was fraudulently obtained and actually belonged to her. In doing so, she falls into a long line of sovereign citizenry gurus who peddle fantastic realities and myths, said Ryan Lenz, a senior writer at the Southern Poverty Law Center’s Intelligence Project.

The Washitaw group, which is made up of African Americans, is part of a larger movement of sovereign citizens in America — a phenomenon that has risen with the economic downturn and the influence of the Internet. Generally, they believe they are above all city, state and federal government laws. They dismiss governments as operating illegally, and they do not believe they have to pay taxes or respect law enforcement officials. 

Police believe that Gavin Eugene Long, the gunman who killed three police officers and wounded three others in Baton Rouge, La., on Sunday, was in the city for several days before he carried out his deadly ambush, Col. Michael D. Edmonson, superintendent of the Louisiana State Police, said during a news conference Monday.

"It was a calculated attack against those who work to
protect the community every single day," Edmonson said.

"We believe that while this individual was in the city he was looking for locations to specifically target police officers," he said. Civilians were walking through the area where Long shot police officers, Edmonson said, and he did not shoot at any of them.

Democratic presidential candidate Hillary Clinton condemned the killing of police officers in Baton Rouge, La., and Dallas as she addressed the NAACP in Cincinnati, and called for reforms to the criminal justice system. 

"Killing police officers is a terrible crime," she said. "Anyone who kills a police officer and anyone who helps must be held accountable."

"Perhaps the best way to honor our police is to follow the lead of police departments across the country who are striving to do better," she continued.

Texas Governor Greg Abbott's office proposed a measure on Monday that would classify crimes committed against law enforcement officers "out of bias against the police" as hate crimes.

“At a time when law enforcement officers increasingly come under assault simply because of the job they hold, Texas must send a resolute message that the State will stand by the men and women who serve and protect our communities,” Abbott said in a statement.

Louisiana legislators passed a similar bill earlier this year.

Deputy Brad Garafola, 45, had been with the East Baton Rouge Sheriff's Office for 24 years and was working in Civil Processing-Foreclosures. At the time he was killed, he was trying to save one of the wounded Baton Rouge police officers, according to sheriff’s spokeswoman Casey Rayborn Hicks.

“He was on his way to the officer when he was shot,” Hicks said.

“This guy was just not a kook out there,” Baton Rouge Mayor Kip Holden said Monday of the gunman in the deadly attack on law enforcement. “If you go back and look at his military background, if you look at how he planned this thing out, some are saying that he was in Baton Rouge several nights even before this happened.

"So we’re finding out somebody that was methodical and planning and really an outright murderer," Holden said in an interview Monday with CNN. "Somebody who knew the movements of police officers, that knew how to position them so they could be within range of then killing them.”

The mayor said some people were coming forward about suspicious activity they had seen, and investigators had received tips on other people who might have been involved.