Last week, a drug task force with the Ross County sheriff’s department executed a search warrant on a trailer in Chillicothe, Ohio. They expected to find a large cache of weapons and drugs.

But after detonating a flash grenade and entering the trailer, they found a 35-year-old woman, Krystal Barrows, dying of a gunshot wound to the head. Weapons and heroin were also found, and six suspects arrested, according to The Chillicothe Gazette. Barrows later died from the wound.

A police investigation determined that the fatal shot had come from the weapon of Sgt. Brett McKnight. According to a police press release, the news came as a surprise to McKnight, who was allegedly unaware that he had even fired.

The department suspects that McKnight fired his weapon by accident, at the exact moment that the flash grenade was detonated. Flash grenades are used to create confusion for suspects as police initiate a raid, although in this case, the police were just as confused as the inhabitants of the trailer.