Glass said a man and three young children had been escorted from the home where the shooting occurred.
"I just happened to be in here when this happened," Glass said about his garage. "To think he could have rolled under my door or needed a car or needed to hide is crazy. It's freaking me out."
From Ladera Ranch, police said the gunman headed north and within 30 minutes carjacked a Dodge pickup truck in Tustin, about 20 miles away. The driver was uninjured, but a bystander was hit by gunfire and taken to a hospital.
The suspect then began firing at vehicles in the area where Interstate 5 and State Route 55 connect.
Three people reported being targeted, including one who suffered a minor injury, Tustin police Lt. Paul Garaven said. Two cars were damaged.
When the truck got low on gas, the gunman stopped at State Route 55 and McFadden Avenue in Santa Ana, stole the BMW and killed the driver, Bertagna said.
The shooter then drove to a Tustin business called Micro Center and carjacked another small truck, killing one person and wounding another, Garaven said.
Officers trailed the gunman to Orange, a city about five miles away.
As they closed in, the man got out of the vehicle at a busy intersection and shot himself, police said.
A shotgun was recovered at the scene.