Angel Granados-Diaz, 19, has been charged with two felony counts of possession of a weapon in a public building, as well as possession of a loaded firearm in a public place and recklessly endangering another person, both misdemeanors.
Through an attorney, he entered a plea of not guilty. His case next heads before a grand jury. If indicted, he'll return to court next week.
On Monday, Granados-Diaz entered the courtroom, his arms behind his back, wearing a green anti-suicide smock and black-rimmed glasses. He spoke with an attorney for several minutes, at times nodding along.
Granados-Diaz has no known criminal history, according court documents filed Monday. The documents also show Granados-Diaz declined to be interviewed by police.
He is being held on $500,000 bail.
Monday was Granados-Diaz's 19th birthday.
Around noon Friday, Granados-Diaz entered Parkrose High School carrying a shotgun, police said. They're still investigating whether shots were fired.
Parkrose football coach and former University of Oregon wide receiver Keanon Lowe confronted Granados-Diaz.
Over the weekend, Lowe recounted to Good Morning America how he stopped a potential shooting.
“I lunged for the gun; we both had the gun. We had four hands on the gun," Lowe said. "Students are running out of the back of the classroom. And I’m just trying to make sure that the end of the gun isn’t pointing toward where the students are turning. But also, not pointed at myself."
Lowe said he was able to get the gun with his right hand while holding Granados-Diaz off with his left.
"And calling for a teacher to come grab the gun from me,” he said.
Lowe said he believes he was in that classroom for a reason and thanked God that no one got hurt.
Portland Police said its behavioral health unit is working on the case. That could mean the bureau is also investigating whether mental health issues could be a factor.
School resumed as normal on Monday at Parkrose.
In a letter to parents, Superintendent Michael Lopes-Serrao said there would be additional counseling support for staff and students all week as well as enhanced security.
Over the weekend, the school held its prom after school officials considered canceling it. District officials said they decided to let the event proceed because it was important for students to connect with their friends.