Authorities reported Friday that the Ventura County Sheriff’s sergeant killed during the mass shooting at the Borderline Bar & Grill in October was struck by "friendly fire" during the firefight with the gunman.

Sergeant Ron Helus was struck by five rounds from the suspect’s gun and a sixth round from the rifle of a California Highway Patrol officer. It was that sixth round which struck Helus in the chest and heart and ultimately killed him, according to CBS News .

When Helus arrived to the scene of the shooting, he heard gunfire coming from inside the bar, which was occupied by nearly 200 college students. He and a California Highway Patrol officer immediately made entry into the bar and confronted the shooter.

"Today I'm deeply saddened to inform you that Sergeant Helus was also struck by a sixth bullet, which we now know through forensic analysis from the FBI's crime laboratory, was fired from the CHP officer’s rifle," Sheriff Bill Ayub said at a news conference.

"It is also important to note that the news I have shared with you today, in no way diminishes the heroic actions both men exhibited at the Borderline," Sheriff Ayub added.