PHOTO: Man accused of killing Border agent arrested

Border Patrol agent Robert Rosas (left) was murdered July 29, 2009 while on duty. Marcos Manuel Rodriguez Perez (right) has been accused of the murder. (Tijuana Police / April 11, 2011)

SAN DIEGO -- A second man accused of murdering U.S. Border Patrol Agent Robert Rosas Jr. in 2009 was arrested in Tijuana Monday, police said.

Marcos Manuel Rodriguez Perez, 26, was captured Monday in the La Mesa section of Tijuana, said director of Tijuana police Adrian Hernandez Perez. He is one of three men believed responsible for ambushing and shooting Rosas near Campo, about 60 miles east of San Diego.

Last year, 17-year-old Christian Daniel Castro Alvarez admitted entering the United States illegally with the intent to rob a Border Patrol agent. He was sentenced to 40 years in prison for Rosas' murder.

Authorities are still looking for a third suspect.

Rosas was patrolling alone in his vehicle about 9 p.m. July 29, 2009. He was working a busy corridor for illegal immigrants and marijuana smugglers. He reported to other agents that he was tracking a group of illegal immigrants near the fence along the international border.

Investigators said the three men lured Rosas into a secluded area where he was ambushed and disarmed. Court records show that Castro held Rosas at gunpoint while the others searched his vehicle.

Nearby agents heard gunshots, but by the time they arrived Rosas was dead.

An autopsy report showed the father of two had been shot nine times, with several rounds to the head.

Before joining the agency in 2006, Rosas was a state prison guard for six years and a reserve officer in the El Centro Police Department for two years.

Tony Duarte, a close friend and fellow agent, said Rosas was such a familiar face around the city that people called him the mayor.

"Robert knew everyone in El Centro, and when I say everyone, I mean everyone," he said.