Those wounded, including at least one who was critically hurt, were being treated in hospital after the shooting at Seattle Pacific University, after America's latest bloody gun rampage.
Seattle Police Department described how the gunman opened fire in a lobby of a science building on the campus.
"Police have one suspect in custody, an adult male who was subdued after being pepper-sprayed by a student security guard," the police statement added.
Initial reports suggested there were two gunman, but police said that proved false.
One student recounted hearing a loud bang from next to the classroom he was in.
His teacher initially thought it was a science experiment, but someone went out and came back saying: "I think someone's been shot."
"So we turn off the lights we lock the door and we close the blinds," the student, identified as Blake, told KIRO 7 TV.
"I was scared for about a minute," he added, recalling hearing shouting and someone running past the door.
After a couple of minutes, "cops come in through another classroom which was connected to ours and they escorted us out.
"I just saw piles of blood on the ground, just scattered throughout the lobby. And I actually stepped in a puddle ....
"I saw someone was on the ground. Someone was on top of them, their hands behind their head."
Police spokesman Chris Fowler described how the young male gunman was taken into custody after opening fire in the lobby of a building on the campus.
He began to reload his gun when a student who was monitoring the building "confronted the shooter (and) was able to subdue the individual," Fowler told reporters, without directly confirming the one death.
"Once on the ground, other students jumped on top of them and they were able to pin the shooter to the ground until police arrived."
The shooting came less than two weeks after a mentally unstable 22-year-old opened fire at a campus in Santa Barbara, California, killing six people before turning the gun on himself.
School shootings have become a tragic periodic occurrence in the United States in recent years.
They include the December 2012 massacre in Newtown, Connecticut that left 20 small children dead, and the Virginia Tech shooting in April 2007 in which 33 died, including the gunman.