The man, who wasn't at student at the school, allegedly entered the Otto Miller Building at about 3 p.m. and opened fire, shooting three people before other students subdued him.
Annie Nguyen, a woman who worked with Ybarra at a gym said that though the suspect was interested in guns, she wouldn't have guessed he would be responsible for such a shooting.
"So we worked with each other for about two, three months," she told KCPQ. "He was an amazing friend. Good worker. He was really calm and nice. If you know him, you would not think he would do it, because... he's just not that type, that would do something like that."
Surveillance footage of the incident showed a building monitor used pepper spray to subdue Ybarra before knocking him down.
"Once on the ground, other students jumped on top of them and subdued the shooter," Seattle Police Capt. Chris Fowler said.
"The students acted without regard for their own safety," said university president Daniel Martin.
Four people were injured in the shooting, one of whom, a 19-year-old man, died upon arriving at Harborview Medical hospital.
A 22-year-old woman, Sarah Williams, was in critical condition after five hours of surgery. One man in his 20s was treated and released. Jon Meis, the monitor who pepper sprayed Ybarra, was also treated and released.
Police said Ybarra confessed to the shooting. They haven't found a connection between him and the private Christian university.