Newport Beach police spokeswoman Kathy Lowe identified the suspect on Tuesday as Stanwood Fred Elkus of Lake Elsinore. His bail was $1 million.
Police say Elkus shot and killed Dr. Ronald Franklin Gilbert on Monday afternoon at the medical office near Hoag Hospital. Gilbert, a 52-year-old Huntington Beach resident, was a urologist.
Police say as many as seven shots were fired, but no motive was released.
Becky Calderwood said she works two doors down from the office where the shooting took place, and said the gunman was a patient.
"I sit right at the front desk, I would have caught the first bullet," Calderwood told the Times.
No one else was injured or targeted, Lowe said. "It does appear to be an isolated incident," she said.
Detectives were interviewing employees and patients in the building.
Kristen Cotty, who works as an office supervisor at a lab one floor above, said she thought the gunfire was construction noises.
"What's going on with the world today?" she told the Orange County Register. "I mean, schools, now I got to worry about going to work. This has got to stop."