A former student linked to the shooting deaths of several people at a small Christian university in Oakland, Calif., was upset at the school administration for dismissing him earlier in the year, the city police chief said today.

A man walked into the single-storey building that houses Oikos University on Monday, took a receptionist hostage and went looking for a particular female administrator, Oakland police Chief Howard Jordan told CNN's Early Start.

"So far we know that the motive is he had been upset with the members or the administration of the school and we're trying to confirm some of the things he told us… He was upset at the school and he was looking for this one particular administrator that he wanted to seek revenge on."

The man then went into a classroom, lined up some students, and shot them one by one, Jordan said.

"We don't believe that the victims had any opportunity to resist, any opportunity to surrender. This was a calculated, cold-blooded execution in the classroom," he told CNN.

All within an hour Monday, police allege 43-year-old One L. Goh walked into the small religious school and began a rampage that left seven people dead and three people wounded, trapped some in the building and forced others to flee for their lives.A teacher from Oikos University who was not working Monday walks away from the scene of the multiple shooting. (Beck Diefenbach/Reuters)

Soon after the shooting, heavily armed officers swarmed the tiny college of fewer than 100 students in a large industrial park near the Oakland airport. For a time, police believed the gunman could still be inside. But he wasn't.

Instead, officers said, he apparently drove about five kilometres from campus before surrendering to officers inside a supermarket. He has yet to face any charges.

911 call alerts police

Those connected to the school, including the founder and several students, described Goh as a former nursing student. The chief said he is a South Korean national.

Police first received a 911 call at 10:33 a.m. local time Monday reporting a woman on the ground bleeding. As more calls came in from the school, the first arriving officer found a victim suffering from a life-threatening gunshot wound, he said.

More officers arrived and formed a perimeter around the school on the belief that the suspect was still inside, he said.

"Potential victims remained inside the building either trapped by a locked door which officers were unable to open," Jordan said. Others were unable to flee because they were injured, he said.

Jordan said there were about 35 people in or near the building when gunfire broke out. Of the seven fatalities, five died at the scene and another two at the hospital. The wounded victims are in stable condition, and at least one person has been released from the hospital.

"This unprecedented tragedy was shocking and senseless," Jordan said.

When asked by CNN why the shooter targeted students, Jordan said it was unclear.

"He just felt a certain urge to inflict pain on them. He gave us no reason why he did that. He just wanted to get back at the administration for dismissing him earlier in the year."

Police have not yet recovered the weapon used, but there is enough ballistic evidence to suggest it was a semi-automatic calibre handgun, Jordan told CNN.

The district attorney will be looking at the case Wednesday, after which charges may be laid, he added.

Gunshots heard

Art Richards said he was driving by the university on his way to pick up a friend when he spotted a woman hiding in the bushes. He pulled over, and when he approached her, she said, "I'm shot" and showed him her arm.

"She had a piece of her arm hanging out," Richards said, noting that she was wounded near the elbow.

As police arrived, Richards said he heard 10 gunshots coming from inside the building. The female victim told him that she saw the gunman shoot one person point-blank in the chest and one in the head.

Tashi Wangchuk, whose wife attended the school and witnessed the shooting, said he was told by police that the gunman first shot a woman at the front desk, then continued shooting randomly in classrooms.

Wangchuk said his wife, Dechen Wangzom, was in her vocational nursing class when she heard gunshots. She locked the door and turned off the lights, Wangchuk said he was told by his wife, who was still being questioned by police Monday afternoon.

The gunman "banged on the door several times and started shooting outside and left," he said. Wangchuk said no one was hurt inside his wife's classroom, but that the gunman shot out the glass in the door. He said she did not know the man.

"She's a hero," he said of his wife.

Television footage showed bloodied victims on stretchers being loaded into ambulances. Several bodies covered in sheets were laid out on a patch of grass at the school. One body could be seen being loaded into a van.

Myung Soon Ma, the school's secretary, said she could not provide any details about what happened at the private school, which serves the Korean community with courses from theology to Asian medicine.

"I feel really sad, so I cannot talk right now," she said, speaking from her home.