Cesar Guzman on Tuesday resolved to chase down the driver of a minivan he said he saw jump a curb and fatally hit a man before driving off.
Guzman said he persuaded the man to pull over and surrender his keys after the collision in the 800 block of East McFadden Avenue in Santa Ana, police said.
"I pulled alongside and yelled 'stop' in Spanish," said Guzman, who works as an auto mechanic.
The 24-year-old victim was identified as Marcello Bisarello of Santa Ana. Police say he was living in a transitional home. He was sitting on a curb when he was struck.
"Somehow (Guzman) got the driver to pull over, and then somehow he got him to surrender his keys," said Santa Anta Police Cpl. Anthony Bertagna.
Police said it was the remarkable act of bravery by a good Samaritan that allowed police to nab the suspect, identified by police as Ramon Horta-Jaime, 55, of Santa Ana. Horta-Jaime failed a field sobriety test and was arrested on suspicion of vehicular manslaughter, police said. He had a prior DUI arrest, police said.
"These guys are given chances to get back in society and it's just unfortunate that this incident happened," said Joe Vargas, who knew the victim.
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Guzman, 29, had dropped off his passenger at the scene of the collision to try to help the man who was struck, but he was beyond help and declared dead when emergency responders arrived.
The suspect stopped a few blocks away near a school, Bertagna said.
Residents of a nearby transitional living home confirmed that the dead man was one of the 10 who lived there.
"I can't even put to words what his family would be feeling," said Dolores Vargas, who knew the victim.
Vargas, who identified herself as the man's caregiver, said he liked to sit on the curb, and returned to the spot despite repeatedly being told it was dangerous.
Vargas said she had been unable to reach the young man's mother. Orange County Coroner's officials had yet to contact the family.
Police said because of his prior DUI conviction, prosecutors could have the option of charging Horta-Jaime with second-degree murder.