KBL Plumbing Co.'s Jeremy Lewis, 26, of Fullerton was working at the Fairfield Inn on Edinger Avenue near the 55 Freeway in Tustin when he was shot and killed by Ali Syed, police said.
Shane Caporaso, a foreman for the company, rushed to intervene and was shot in the arm. He has since been released from the hospital.
"We lost a good employee, and another one of our employees was hurt," said Kim Munson, director of operations for KBL Plumbing.
"Several employees witnessed it. Shane is a hero, in our opinion."
The rampage began before dawn Tuesday at a home in Ladera Ranch and ended 25 miles to the north during the early morning rush hour, police said.
Courtney Aoki, 20, of Buena Park was shot multiple times early Tuesday in the home that Syed, 20, shared with his parents, said Orange County sheriff's spokesman Jim Amormino.
Syed killed two more people during carjackings, injured at least three more, and shot up cars zooming down a busy freeway interchange before committing suicide with his shotgun as police closed in, authorities said.
The shooter forced one commuter stopped at a stop sign out of his BMW, marched him to a curb and shot him three times from behind as shocked witnesses looked on, Tustin police Chief Scott Jordan said.
The motive for the shootings remained unclear.
Syed had no criminal history and no history of mental illness or mental disability, said Lt. Paul Garaven, a Tustin police spokesman.
His parents did not recognize the woman who was shot to death in the Ladera Ranch home, he said.
Syed's parents rushed outside and called police at 4:45 a.m. Tuesday after hearing the gunshots, but Syed had already sped off in his parents' black SUV.
From Ladera Ranch, the gunman headed north and pulled off the 5 Freeway in Tustin, about 20 miles away, with a flat tire, police said.
There he fired at and wounded a man in a car, then carjacked a vehicle from a man at a gas station and got back on the freeway, where he fired at commuters, authorities said.
The shooter then exited the freeway in nearby Santa Ana and carjacked a BMW, killing driver Melvin Lee Edwards, 69, of Laguna Hills.
Syed took Edwards' BMW and next popped up near the Tustin hotel, where police said he killed Lewis.
"It's devastating. My employees were in the lot," Munson said. "They were there when Jeremy got shot. They called Shane and he got in a truck to drive to the offsite parking lot to see if he could help. The gunman shot Shane and took his truck."
KBL Plumbing is in the 12000 block of Santa Margarita Court.
Syed took the utility truck and fled to Orange, this time with California Highway Patrol officers in pursuit. He jumped from the moving truck at an intersection about five miles away and shot himself in the head.
Syed, a part-time community college student who ultimately committed suicide, Amormino said.
A 12-gauge shotgun used in the killings belonged to Syed and was purchased by his father about a year ago, he said.
The Associated Press contributed to this report.