The day before Gary Martin killed five colleagues at an Illinois manufacturing company, he issued a warning to his coworker: “If I get fired, I am going to kill every motherfucker in here. I am going to blow police up.” Martin’s confession was released in a Friday report to the Aurora and Naperville police departments that found officers at the scene were justified in their use of force when they fatally shot the 45-year-old during the Feb. 15 incident. “Based upon a review of the investigation, all officers at the scene of this incident had the reasonable belief that the deadly force they employed was necessary to prevent death or great bodily harm to themselves and other individuals as they attempted to locate and arrest the offender,” Kane County State’s Attorney Joseph McMahon said.

According to the nine-page report, the Henry Pratt Co. employee told investigators he knew Martin had a firearm in his vehicle, but that he didn’t report his former colleague’s comments because he was always making “off the wall” statements. Investigators allege, based on facility surveillance video, that Martin brought the gun into the building when he came to work for a disciplinary meeting over his refusal to wear safety glasses.