A private security guard was not supposed to have the gun he used during the shooting at STEM School Highlands Ranch in May, a Colorado news outlet is reporting.

STEM had requested that BOSS High Level Protection send unarmed guards when they hired the company in 2018, according to emails obtained through an open-records request by The Colorado Sun.

However, the BOSS guard, whose name was not revealed by The Colorado Sun, was armed when the shooting occurred in May. The guard was able to detain one of the shooters, but accidentally fired his gun at a sheriff’s deputy. That shot hit and wounded a student who was not involved, according to court documents relating to the arrest of the alleged shooters.

The school told The Colorado Sun that they will not employ BOSS for the next school year due to the ongoing investigation, but declined to comment on whether future guards will be armed.

“BOSS will not be providing services to STEM this upcoming school year,” STEM spokesman Chris Arnold said.

“For the upcoming school year, we were able to arrange for a full-time school resource officer from the Douglas County Sheriff’s Office, and will continue to supplement that level of security with private security, including off-duty police officers.”