(CNN) -- Mourners packed church pews Tuesday at a memorial service for seven victims slain in a shooting rampage at a small religious college in Oakland, California.
"We realize that at this time we have to draw together, uniting for peace, praying for peace in our city, and praying to stop the violence," said a woman who introduced various parts of the service.
Meanwhile, authorities continued searching for the weapon a gunman used Monday when he killed seven people execution-style at Oikos University.
Accused shooter One Goh gave some details to investigators about Monday's attack, but refused to say where he disposed of the gun, police said.
Investigators had narrowed their search for the weapon and were combing a shoreline park area Tuesday, police spokeswoman Johnna Watson told reporters.
Forensic investigators were still at the scene of the shooting Tuesday, she said.
Police plan to present the case to the district attorney for possible charges sometime this week, she said.
"It's a large investigation. We want to be thorough," she said.
Goh was being held Tuesday in Alameda County's Santa Rita Jail pending an initial appearance in court this week.
The 43-year-old former student at the college "does not appear to be remorseful at all," Oakland Police Chief Howard Jordan said.
Goh told authorities that he was upset about being expelled from Oikos University this year, Jordan said.
Investigators believe Goh walked into the single-story building housing the university Monday morning, took a secretary hostage and went looking for a particular female administrator, who was not there, Jordan told CNN.
Goh took the secretary into the classroom, but when he realized the administrator was not there, he shot her 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.
"He planned this several weeks in advance," Jordan told KTVU on Tuesday. "He was so upset he went out and purchased a weapon and had every intent to kill people yesterday."
All three of those wounded were released from Oakland's Highland Hospital on Monday night, spokeswoman Monique Binkley Smith said Tuesday.
Oakland Mayor Jean Quan condemned the violence.
"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."
Investigators have determined that the gun they believe Goh used was obtained legally in California, but details about the weapon's purchase were still under investigation, Watson said.
Harrowing descriptions of chaotic scenes inside and outside the college emerged Tuesday.
Audio recordings of police radio exchanges released Tuesday include a dispatcher describing reports of shots coming from inside the building.
"People are running out, screaming," she says.
"There's a female bleeding down on the ground, face down on the concrete," a dispatcher says.
An officer at the scene describes a man who has a gunshot wound to his head.
"We were able to extricate one body, a victim from the building, the victim still has a faint pulse. We're waking her up now," another officer says.
Art Richards told CNN he was on his way to pick up a friend and thought the commotion outside the school 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 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."
Brian Snow said he was at a nearby credit union when shots rang out.
"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," he said.
Meanwhile, inside the college, survivors hid behind locked doors or desks as gunfire erupted.
Tashi Wangzon said that his wife, a student there, heard the shots, then 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)."
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 and heard someone yell, "He's got a gun." Garcia said he got his students out of the building while the gunfire continued.
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 of Monday's shooting 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.
Quan, Oakland's mayor, 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.
Community and faith leaders were scheduled to attend Tuesday's memorial, and they hope to develop a strategy for dealing with the situation, said June Lee, executive director of the Oakland-based Korean Community Center of the East Bay.
"We're looking for a way to help the families and the community that are impacted by this incident," she said.
Civic and church leaders will try to come up with a community strategy to deal with the tragedy, she said. But she stressed the importance of not stigmatizing Koreans or Asians.
"This is all new to us. We don't want to stigmatize whatever the issue is. ... We need to identify the issues first," she said.
CNN's Michael Martinez, Sara Weisfeldt, Matt Smith, Alan Duke, Paul Vercammen, Dan Simon and Augie Martin contributed to this report.