SEATTLE (CBS News) -- A gunman opened fire Thursday afternoon in a building at Seattle Pacific University, killing one person and wounding three others before one student attacked him with pepper spray and several others tackled him, police said.
The shooting happened about 3:30 p.m. in Otto Miller Hall, CBS affiliate KIRO-7 News reported.
Seattle police said the suspect, who was armed with a shotgun and a knife, entered the building and opened fire in the foyer. The man, who had additional rounds with him, began reloading the shotgun.
At that point a student who served as a building monitor confronted the shooter and pepper-sprayed him, grabbed his gun and pushed him to the floor, police said.
"The shooter began to reload his shotgun and the student building monitor inside the hall confronted the shooter and was able to subdue individual," police Capt. Chris Fowler said. "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."
Police said the suspect was a man "approximately 26 years old" and was not a student at the school. His name was not immediately released and police did not offer a possible motive.
Paramedics transported four victims to Harborview Medical Center. A 20-year-old man who had suffered gunshots wounds to his upper body was pronounced dead at the hospital, police and hospital officials said.
A 20-year-old woman who suffered a gunshot wound to her upper body was in critical condition was undergoing surgery, hospital officials said.
Two other men, ages 24 and 22, were in satisfactory condition. Police said Thursday night that one had suffered "pellet-type wounds" to his neck and chest and the other had "minor wounds to the abdominal region."
"This is a tragic moment for Seattle, and it's a tragic moment for America," Seattle Mayor Ed Murray told reporters.
"Today should have been a day of celebration at the end of the school year at SPU. Instead it's a day of tragedy and loss," he said.
The campus, located about 10 minutes from downtown Seattle, was placed on lockdown as first reports of the shooting were received. Traffic around the school was blocked.
"Campus is in lockdown due to shooting near Otto Miller Hall. Classes are suspended. Please do not come to campus," the university posted on its website.
Police said they went through every room in the building and found several students who were hiding.
The lockdown was later lifted a few hours later and a special prayer service was being held Thursday evening.
"Our heartfelt prayers are with the entire community," the university posted on its website.
Police at one point said there were two suspects in custody, but later said there was only one person under arrest and no other suspects were being sought.
The building houses the school's math, computer science, engineering, physics and science education departments.
Students said they were shocked by the violence at the Christian university, which has about 4,200 undergraduate and graduate students.
"Right away it was like my heart had sunk because it is such a safe place and close, tight-knit community," senior Nate Johnson told KIRO. "I have a lot of friends who are science majors and engineering majors who would have been in Otto Miller, a lot of friends in the athletic building, which is just across the street."