Police said the suspect, a 43-year-old Korean-American, surrendered at a Safeway grocery store several miles away from the scene at Oikos University in Oakland after the deadliest US school shooting in five years.
He was named by police as One Goh, a former student at Oikos, which has links to the Korean-American Christian community. Police described the man as both a Korean national and a naturalised American citizen from Korea. They said they believed he used a handgun and acted alone.
Police did not immediately offer a motive for the rampage -- which came just over a month after a student gunman in Ohio opened fire in a high school cafeteria, killing three students. It was not immediately clear why Goh had left the school.
"We haven't interviewed him yet, so we're still trying to put those pieces together," Oakland police chief Howard Jordan told a news conference.
Witnesses said the gunman entered a reception area of the college at mid-morning and opened fire before walking into one of two classes in session and spraying the room with bullets.
Paul Singh, whose 19-year-old sister Devinder Kaur was shot in the arm during Monday's rampage, told Reuters that according to his sister, the man was a former student who showed up to class for the first time in four months.
"'Get in line and I'm going to kill you all,' is what he said this morning, my sister told me. They thought he was joking at first,'" Singh said.
Tashi Wangchuk said his wife, 28-year-old Dechen Yangzom, was in the second classroom when she heard gunfire.
"Out of instinct, she locked the door and turned off the lights then the guy came and banged on the door and shot several rounds at the door and then he left," Wangchuk said. "The police said what she did was heroic."
Oakland police spokesman Johnna Watson said at least seven people had been killed and three others wounded.
It was the deadliest outburst of gun violence at a US school since a Virginia Tech student shot and killed 32 people in a 2007 massacre on that campus before killing himself.
Images from local TV stations showed frightened students and staff running from the school, located in a light industrial area near Oakland International Airport, as police and SWAT teams carrying assault rifles surrounded the area.
Hours later, two bodies remained on a grassy area outside the school, covered by yellow plastic sheeting.
Agents from the US Bureau of Alcohol, Tobacco and Firearms were on the scene, along with dozens of local police.
"No American mayor wants to have this situation," Oakland Mayor Jean Quan told a news conference. "This is the kind of incident that hurts the whole community."
Angie Johnson, 52, told the San Francisco Chronicle newspaper she was doing errands nearby when she saw a young woman run from the college with a bloodied right arm, crying "I've been shot, I've been shot."
Johnson said the wounded woman told her the shooter was a man in her nursing class who shot one person at point-blank range before spraying the room with bullets.
Nearby businesses were evacuated and shut down for the day as officers searched the school and surrounding area. A spokeswoman for nearby Highland Memorial Hospital declined to comment on the condition of victims being treated there.
"As you may have heard, the suspected shooter in today's deadly shooting at Oikos University on Edgewater Drive is in custody, and it appears he acted alone," a brief statement from the Oakland city administration said.
"The surrounding area is still cordoned off, but police have advised that no imminent public safety threat appears to exist in the immediate area," it said.
Oikos, which offers programmes in theology, nursing, music and Asian medicine, describes itself on its website as having been started to provide the "highest standard education with Christian value and inspiration."
"The tragic loss of life at Oikos University today is shocking and sad," California Governor Jerry Brown said in a statement released through his office.
"Our thoughts and prayers go out to the victims, their families and friends and the entire community affected by this senseless act of violence."
