DENVER — A security guard credited with capturing one of the two suspects in this week’s suburban Denver school shooting fired his weapon inside the school, a law enforcement official with knowledge of the case told The Associated Press on Thursday.

The security guard has not been identified but is a former Marine who has stayed out of the public eye since Tuesday, when two suspects opened fire at the STEM School Highlands Ranch, killing one student and injuring eight.

Two news organizations cited anonymous sources reported that authorities are investigating whether the guard mistakenly fired at a responding sheriff’s deputy and may have wounded a student.

The law enforcement official spoke to The Associated Press on anonymity because the official was not authorized to make information public. The official did not address whether anyone was hit by the security guard’s firing.

An attorney for the guard declined to directly answer questions Thursday about the media reports.

But the attorney, Robert Burk, said his client acted in the best interests of protecting the children at the school and helped resolve the situation without further bloodshed.

“He ran there as quick as he could and took what I think is decisive action that helped save lives,” Burk said.

Three students have been hailed as heroes for disarming one of the suspects during Tuesday’s shooting. One of them, Kendrick Castillo, was shot and killed during the struggle and a second, Joshua Jones, is recovering at home after being shot twice.

The security guard ran to the area of the shooting and apprehended one suspect in a hallway, said his employer, Grant Whitus of Boss High Level Protection, a former SWAT team leader who responded to the 1999 Columbine High School shooting.

“He doesn’t even realize how many lives he saved by stopping a school shooting,” Whitus said.