Barton Chavez, an Antioch resident, was shot multiple times at the intersection of West Madill Street and William Reed Drive around 12:20 p.m., Antioch police Lt. Diane Aguinaga said.
No arrests had been made in the case as of Thursday morning.
The gunfire startled neighbors and staff at Marsh Elementary School, which is less than a block from the site of the murder.
Neither the elementary school nor nearby Antioch Middle School or Antioch High School was put on lockdown after the shooting, Antioch Unified School District Stephanie Anello said.
However, campus and school district personnel were tasked with guiding Marsh Elementary students as they left the campus at the end of the day.
"We wanted to block as much of the view as possible for the little kids and make sure they had a safe passage," Anello said.
Anthony Vieira, who lives near the scene of the shooting, said he "jumped up" when he heard loud noises and then saw a young man lying in the street. Soon after, police arrived and covered the man's body with a yellow tarp, he said.
Vieira, who is retired, said he has noticed an increase in crime in the neighborhood over the past few years.
Antioch police also responded to a second shooting Wednesday around 6:45 p.m. in the 2300 block of Manzanita Way, less than a mile from where the murder occurred. Two victims were injured by the gunfire but are expected to survive, Aguinaga said.
She said neither victim was cooperating with the police investigation.
The evening shooting does not appear to be connected to the homicide, Aguinaga said.