Syed then crossed the street to a Mobil gas station, where he approached the driver of a pick-up and asked for his keys, Jordan said.
"He says something to the effect of, 'I've killed somebody. Today's my last day. I don't want to hurt you. Give me your keys,'" he said. "He hands over the keys and he gets in the truck and leaves."
Syed got back on the freeway, where he pulled to the side of the road at the busy I-5 and State Route 55 interchange and began firing at commuters, Jordan said.
One driver was struck in the mouth and hands. He didn't have a cellphone, but was able to drive home and call police. Two other cars were hit but their drivers weren't injured, Jordan said.
"All of this is happening so quickly," he said, estimating that Syed shot at drivers from the side of the freeway transition for about a minute.
The shooter then exited the freeway in nearby Santa Ana but ran the curb and got his car stuck, authorities said.
He approached Melvin Edwards, a 69-year-old from Laguna Hills who was on his way to his Santa Ana business, as Edwards sat in his BMW at a stop sign. Syed forced Edwards to get out of his car, marched him across the street and shot him three times, including in the back of the head and the back, as horrified drivers looked on, Jordan said.
"They tried to get away. They saw what was going on, they tried to get away and they called police," he said.
Syed took Edwards' BMW and next popped up at the Micro Center, a Tustin business, where he shot and killed construction worker Jeremy Lewis, 26, of Fullerton. Lewis' co-worker rushed to intervene and was shot in the arm, Jordan said.
Syed took the second construction worker's utility truck and fled to Orange, this time with California Highway Patrol officers in pursuit. He jumped from the moving utility truck at an intersection in Orange, about five miles away, and shot himself immediately, Jordan said.
A shotgun was recovered at the scene.
A message left at Syed's parents' home wasn't immediately returned on Tuesday.
Associated Press writers Sue Manning and Shaya Tayefe Mohajer in Los Angeles contributed to this report.