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Ted S. Warren, Associated Press
Brady Olson, right, the teacher at North Thurston High School who helped subdue a student who had fired a gun in the school on Monday, talks to reporters Tuesday, April 28, 2015 in Lacey, Wash., as he stands with his wife Shara, second from right, and their children Madelyn, 15, left, and Jake, 13. Olson said his first thoughts as he took action were to get the gun away but also to act with concern for the shooter’s well-being.

SEATTLE — Prosecutors have filed five charges in juvenile court against the 16-year-old accused of firing a gun inside his Washington state high school.

No one was injured in Monday's shooting at North Thurston High School in Lacey, about 60 miles southwest of Seattle. A fast-acting teacher tackled the boy after he fired two shots.

The charges filed Wednesday include theft of a firearm, felony harassment, unlawful possession of a firearm, possession of a firearm on school property and illegally discharging a firearm. Arraignment is scheduled for May 11.

Senior Deputy Prosecutor Wayne Graham said these charges carry a standard sentencing range of six to 12 months, but that doesn't include potential firearms enhancements. Graham anticipates there will be further charges filed once the investigation is complete.

"We have many layers of the onion still to get through," Graham said Wednesday.

The prosecutor said he hasn't decided whether to bring any charges against the parents. State law is grey in the area of keeping guns away from children and does not require them to be locked in a safe, Graham said.

For now, the investigation is focused on the school and school victims, he said.

There could be more charges associated with injuries that occurred when a few students fled the scene. For example, two students fell down while running away and were trampled.

Police have 500 witnesses to interview and have been flooded with phone calls from parents and students, Graham said. Once all the interviews are done, they will reassess the charges, he said.

"There could be a number of different crimes depending on what information comes out," he said. "It's just overwhelming the police department right now."

Although the 16-year-old was initially charged as a juvenile, that could change as well, depending on the charges and whether they decide to petition the juvenile judge to move the case up to adult court, Graham said.

The boy has a previous record. He is on active probation from multiple counts of fourth-degree assault with sexual motivation, Graham said.

The boy is being held in Thurston County with bail set at $500,000, and he has been scheduled for a mental health evaluation.

The boy stole the .357 Magnum pistol from his father and brought it to school in a duffel bag, Graham said during a court hearing Tuesday.

Police say the teen fired two shots before being stopped by a group of teachers and administrators in the school commons where hundreds of students had gathered before school Monday.

The boy, a recent transfer to the school, reportedly told detectives that he didn't intend to hurt any other students.