Longmont police are trying to find out what made a student at Silver Creek High School stab his female colleague in the back several times with a pair of scissors Thursday.

The girl, whose identity has not been released, was transported to Longmont United Hospital where she was treated for her seven injuries in the upper back and left arm. She was soon released from the hospital as the wounds were not life threatening.

The incident happened Thursday around 10.30 a.m., when the girl tried to get into her locker between second-and third-period classes. The boy started stabbing her with a pair of scissors in the upper back, Longmont police spokesperson Craig Earhart said in a news release, according to local media sources.

“At the end of the hallway, the victim fell to the floor and the suspect threw the scissors into the wall near where the victim collapsed,” Earhart said.

After the incident, the boy tried to run away but the other students and staff members who witnessed the whole thing stopped him, investigators said.

The boy was arrested on suspicion of attempted first-degree murder, attempted first-degree assault and second-degree assault, all felonies, and was transported to the Longmont Police Department for booking. He will be transferred to the Boulder Juvenile detention facility in Boulder. His name has not been released because he is a juvenile.

The boy and the girl were both ninth-grade students at the school, but investigators said it does not appear that the victim knew her attacker or that there was any issue or exchanges between the two.

“I have no idea. I’ve never seen him before,” the girl answered when a rescuer asked her if she knew the attacker, TimesCall.com reported. The boy, known as “quiet” and “formal,” recently transferred to the school and not many students knew him, the same source said.

Investigators do not know the boy’s reason for the crime, but an investigation is ongoing.