After years in the L.A. street gang world, Ronald Lamonte Barron devoted his life to preventing young people from following in his footsteps.

Barron, a former member of the Mansfield Crips gang that claims territory around Pico Boulevard and La Brea Avenue, was one of a few gang outreach workers who was trusted enough by Los Angeles authorities to counsel young offenders in the jails.

Barron was leaving a bar in his old neighborhood Sunday night with his girlfriend when he noticed a tagger defacing a wall on Pico.

Detectives said he confronted the tagger, who fatally shot him as his girlfriend and others looked on.

The Los Angeles Police Department said surveillance video from nearby businesses captured the killing in the 5000 block of West Pico Boulevard in the Mid-Wilshire district.

The footage appeared to show a gunman wearing dark-colored clothing arguing with Barron in front of “numerous witnesses,” LAPD detectives said.

The suspected gang member, a Latino 20 to 25 years old, approximately 6 feet tall and 180 pounds, then pulled out a pistol and shot Barron multiple times at point-blank range before calmly walking off.

Shot in the head and chest, Barron fell in the middle of the busy thoroughfare. The 40-year-old was pronounced dead at a local hospital a few hours later.

His slaying stunned colleagues at Amer-I-Can, where Barron had worked for more than a decade.

The loss was also felt at City Hall and LAPD headquarters, where officials rely on gang interventionists like Barron to help reduce the grip of gangs in some neighborhoods.

Barron was considered a veteran in the field.

“Very few people reach that level,” said attorney Connie Rice, a prominent civil rights attorney and leader of the Advancement Project, which is providing formal training for gang outreach workers.

“There are a lot of con artists who claim to be interventionists,” Rice said. Barron “was one of the genuine ones. He was dedicated. He was trusted enough to go into the jails. That’s a pretty rare status.”

Authorities don’t believe his work in gang intervention played any role in the killing.

LAPD Cmdr. Andy Smith said Monday that there was “every indication that he was shot because he confronted the man who writing on the wall.”

There have been a string of cases in recent years in which taggers have fatally shot those who dared to call them out.

In 2008, Jose Jorge Perez was fatally shot in East Hollywood after pulling his car over to tell a group of men to stop tagging.

Maria Hicks, a 57-year-old Pico Rivera grandmother, was gunned down in 2007 after she honked her car horn, flashed her lights and followed a tagger who had defaced a wall.

That same year, Robert Whitehead was killed in Valinda after challenging young gang members he caught crossing out another gang’s graffiti on a neighbor’s garage.

Barron played a role in an unusual but lauded program to pass out tens of thousands of bottles of water in the inner city during the hottest days of the year -- an effort to encourage sobriety and stem violence.

He also was an ambassador who traveled the country to spread the word about Amer-I-Can and its contributions to helping at-risk youth.

Over the weekend, Barron had attended a fundraiser for Calvin Hodges, another gang outreach worker who was shot three months earlier in Nickerson Gardens, leaving him partly paralyzed.

Barron “was known for being an educator,” said Marcus “Big Ship” Bell, an intervention worker from Amer-I-Can. “He was really into the kids and really into social change.”

andrew.blankstein@latimes.com

scott.gold@latimes.com