The wounded were taken to Harborview Medical Center, with two patients listed in life-threatening injuries and two others in stable condition, Seattle police said.
The gunman walked into the Otto Miller Building just after 3 p.m. and shot four people, Seattle police said. The gunman then began reloading when staff members were able to disarm him, police said.
Fire officials on the scene originally indicated there were seven wounded besides including the shooter, but have since brought that number down to four victims. There are conflicting reports whether the gunman was wounded.
Witness Briana Clarke was inside Otto Miller Hall when the shots rang out. She was still unsure what was happening when she saw students running down the halls.
"I first heard two muffled shots that I thought were two helium balloons," she said.
Clarke then said she saw injured students inside the building and when she went outside, she saw several more bloodied students.
'When I walked outside and seeing someone down... that was disturbing seeing a bunch of bullets around, the blanks all around and red that was a very disturbing image," Clarke said. "Seeing my friend outside being treated that's was hard to swallow, that a fellow student, that it could have been you."
University counselor Karen Altus was in her office -- less than a block from the crime scene -- when she got an alert about the shooting.
"I'm in my office with four students with the blinds closed. The we're sitting on the floor with the door locked, very scared," she said.
Police officials say one person was in custody on the SPU campus and that officers and medics were on the scene. SPU officials report the campus remains on lockdown.
About 4,270 students attend the private Christian university.