(CNN) -- The man accused of killing seven people execution-style at a small religious college in Oakland, California, "does not appear to be remorseful at all," the city's police chief said Tuesday.
Former student One Goh, 43, told authorities he was upset about being expelled from Oikos University this year, Police Chief Howard Jordan said.
He was upset with some administrators and students and said he had been "picked on" and "wasn't treated fairly," Jordan said.
Investigators believe Goh walked into the single-story building housing the university Monday morning, took a receptionist hostage and went looking for a particular female administrator, who was not there, Jordan told CNN.
Goh took the woman into the classroom, but when he realized the administrator was not there, he shot the secretary and ordered the students to line up against the wall. Not all of them cooperated, Jordan said, and so he began shooting.
"I'm going to kill you all," the gunman said, according to CNN affiliate KTLA.
"This was a calculated, cold-blooded execution in the classroom," Jordan said. The suspect "just felt a certain urge to inflict pain on them," he said.
After the shooting, the man left the classroom, reloaded his semiautomatic weapon and returned, firing into several classrooms, Jordan said.
He ended his rampage by driving off in a victim's car, police said. In all, seven people were killed and three were wounded.
"This happened within minutes," Jordan said. "We don't think the victims had any opportunity to resist, any opportunity to surrender."
The suspect was arrested a short time after the shooting, when he surrendered to police at a grocery store in the Oakland suburb of Alameda, Jordan said.
Goh offered no resistance when arrested, Jordan said, and was "very cooperative, very matter-of-fact, very calm." Under questioning, Goh "remembered very good details" about the incident, he said.
All three of those wounded were released from Oakland's Highland Hospital on Monday night, spokeswoman Monique Binkley Smith said Tuesday.
The college caters to the Korean-American Christian community but also has students from diverse backgrounds. It offers degrees in theology, music, nursing and Asian medicine, according to its website.
The victims ranged in age from 21 to 40 and were from countries including Korea, Nepal, Nigeria and the Philippines, Jordan said. With the exception of the secretary, all the victims were students. Of those killed, six were women and one was a man, but Jordan said investigators do not know whether Goh was targeting women.
The details of the shooting surfaced early Tuesday as police interviewed Goh. He "does not appear to be remorseful at all," and would not tell police where the weapon was located, Jordan said. Investigators plan to search for the gun Tuesday, he said.
Forensic investigators were on the scene of the shooting Tuesday.
Art Richards videotaped the chaotic scene outside the college Monday. He told CNN he was on his way to pick up a friend and thought the commotion was caused by a car accident.
Then, he said, a woman emerged from bushes and told him she had been shot. "I was kind of mind-boggled," he said, but the woman showed him her arm. "She had a good little piece, a chunk of her arm missing."
Police handcuffed one Asian man outside the school, but the woman told authorities he was not the shooter, Richards said.
"Right after that, close to seven, eight, nine shots rang out," he said. "Everybody got down. The police took cover. We took cover."
A few minutes after that, the first body was brought out, he said. "They were just pulling out bodies after bodies."
Jong Kim, a pastor who founded the school a decade ago, told the Oakland Tribune that Goh was a former nursing student.
He was deeply in debt and had tens of thousands of dollars in tax liens, including from the Internal Revenue Service, according to CNN affiliate KGO. Goh's brother, a staff sergeant in the Army, died last year in a car accident while training with the Special Forces, KGO said.
It wasn't immediately clear why Goh had been expelled from the college, Jordan said, but, "We've been told that some of the possibilities are that he was expelled for his behavioral problems, anger management, but nothing specific."
CNN affiliate KTVU reported Goh was an Oakland resident and a frequent visitor at Oakland's Westlake Christian Terrace senior housing, where his parents live.
"(He seemed) just like a really good kid, the kind of kid I want all my residents here to have," Audrey Williams of Westlake Christian Terrace told the station.
A woman who answered the phone Tuesday at Westlake Christian Terrace told CNN she knew nothing about the situation and hung up.
Police expect to present the case to the district attorney for possible charges in the next few days, Jordan said. Goh was being held Tuesday in Alameda County's Santa Rita Jail pending an initial appearance in court this week.
Asked why Goh stopped shooting, Jordan said authorities arrived within minutes of the first 911 call at 10:33 a.m., and investigators believe Goh did not want a confrontation with police.
Oakland Mayor Jean Quan said most of the victims appeared to be from the city's Korean-American community, and the city was working to find multilingual counselors to help survivors.
"No American mayor wants to have this situation," she said. "It seems over the last decade, we've gotten used to seeing senseless mass killings like this, and we'll have to question the availability of guns and the need for other services in our community."
A witness, Brian Snow, said he was at a nearby credit union when shots rang out.
"In Oakland, sometimes things like that happen, but it dies over," he said. But this time, he said, "I went outside and the cops were coming and like 'Don't move, don't move,' and it started getting chaotic. ... A pedestrian came out with a bullet hole, and I was like, 'Getting really crazy right now.' "
He said that after shots rang out, he called the credit union to tell them to lock their doors and also called the nearby restaurant where he works, but "all I could do was just lay on the ground and wait."
Lucas Garcia, who was teaching an English class at the college when the rampage began, told KGO that he counted about six gunshots from a nearby nursing classroom.
Garcia said he heard someone yell, "He's got a gun," and he got his students out of the building while the gunfire continued.
Several survivors, including the wounded, hid behind locked doors or desks as the shooting went on.
Tashi Wangzon said that when his wife, a student, heard the shots, she locked the door to her classroom and turned off the lights.
"The man with the gun later came toward the room and, at the time, he fired several rounds at the door," Wangzon told KGO. "Then he left (when he thought nobody was there)."
Lisa Resler said she encountered Goh as she went into a Safeway in Alameda to pick up groceries.
"He was by the front door," she told CNN. "There's a restroom that's right by the front door of the Safeway. We made eye contact with each other."
She said the man looked "a little bit distraught. He did look like he was a little bit sweaty and a little bit discombobulated."
When she came out of the store, the man was being arrested out front, she said. At the time, she said, she thought he had been caught shoplifting.
California Gov. Jerry Brown, who was Oakland's mayor from 1999 to 2007, called the killings "shocking and sad."
"Our thoughts and prayers go out to the victims, their families and friends and the entire community affected by this senseless act of violence," Brown said in a statement.
U.S. Education Secretary Arne Duncan said Tuesday he was "saddened" to learn of the "senseless violence and loss of life" at the college.
Tuesday evening, a grieving community will hold a memorial service for the victims at the Korean Methodist Church.
Officials said they may have to change the location if the church isn't large enough to hold all those who plan to attend.
CNN's Sara Weisfeldt, Matt Smith, Alan Duke, Paul Vercammen, Dan Simon and Augie Martin contributed to this report.