The Seattle Police Department said via Twitter that Aaron Ybarra, 26, had been booked into King County Jail for the shooting at Seattle Pacific University on Thursday, but did not offer an explanation for any motive for the attack.
The lone suspect, who was not a student, entered an academic building of the university in the late afternoon and shot three people, police said.
He was disarmed as he paused to reload his gun and was pepper-sprayed by a student security guard. A fourth person was wounded in the struggle with the gunman, police said.
"Other students jumped on top of them, and they were able to pin the shooter to the ground until police arrived" minutes later, police Captain Chris Fowler told reporters on the scene.
Americans are engaged in a protracted debate over gun control regulations after a series of shootings in public places such as schools and theaters. On May 24, a 22-year-old gunman killed six people before taking his own life in a rampage across a California college town.
One eyewitness in Seattle, Chris Howard, a 22-year-old junior, told Reuters he was in a classroom when one of the male victims rushed in bleeding from the neck and told students to lock the doors.
Stepping outside the classroom moments later, Howard said he saw the gunman lying on the floor with the student security monitor on top of him, surrounded by bullet shells, and saw a second victim with a tourniquet tied around a bleeding arm, being assisted by another student.
He was armed with a gun and a knife and extra ammunition, police said.
The suspect could face a murder charge, Fowler told an evening news conference.
A representative of Harborview Medical Center in Seattle said four patients from the shooting were brought to the hospital and that one, a man in his 20s, had died.
Two other men, aged 22 and 24, were listed in satisfactory condition, the hospital official said. A woman in her 20s underwent five hours of surgery and was in critical condition, media reported.
One of the men suffered pellet wounds to his neck and chest and the other suffered minor injuries, police said.
NO MOTIVE IMMEDIATELY CLEAR
Further details of the shooting in the upscale Seattle suburb of Queen Anne, a residential neighborhood, were not immediately available.
Another student, Blake Oliveira, 21, who was taking a physics course in Otto Miller Hall at the time, told Reuters he heard a gunshot outside the classroom, followed by the sound of running footsteps, which he presumed to be the gunman.
His professor instructed the students to stay put in the classroom, and the door was locked, Oliveira said.
Seattle Pacific University is a Methodist liberal arts college about 4 miles (6.4 km) north of Seattle's downtown, with about 4,000 students enrolled.
The college website said students are subject to disciplinary action for such behavior as extramarital sex or homosexual activity and for the possession or use of alcohol.
Students could be seen embracing and otherwise consoling one another on campus, some crying as they recounted hearing a gunshot. An evening prayer service was being held at a campus church.
"We're a community that relies on Jesus Christ for strength and we'll need it at this time," said Seattle Pacific University President Daniel Martin.