A lone suspect, who was not immediately identified, entered an academic building on campus in late afternoon and shot four people, then began reloading his gun but was disarmed by university personnel, police said in a Twitter message.
A student, Chris Howard, 22, a junior at the university who was in the building, Otto Miller Hall, at the time, told Reuters he saw the gunman lying on the floor after he had been subdued with a student security guard lying on top of him, surrounded by bullet shells.
Howard said he also saw a gun and a knife lying on the floor nearby.
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, and a 20-year-old woman was listed as critical and undergoing surgery, the hospital official said.
The Seattle Times newspaper put the tally of individuals struck by gunfire at six, but that number could not be immediately confirmed.
Further details of the late-afternoon shooting in the upscale Seattle suburb of Queen Anne, a normally quiet residential neighborhood, were not immediately clear.
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.
He said he also caught a glimpse of blood afterward. His professor instructed the students to stay put in the classroom, and the door was locked, Oliveira said.
The school said on its website that the campus was placed on a security lockdown as a result of the shooting.
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.