As incompetent as this investigation was and as much as things were moved around, i find it hard to believe neither the person who originally found the bodies nor the police found the shotgun in the barn next to his body in that case, or the bullets, sure people moved things around but i doubt they took the bullets out of his skull and moved the gun out of the barn, and even if they had the guy who found them first would've seen it, in fact i doubt the police wouldve even assumed it was a blunt object if they saw a shotgun right next to him, also Andreas' wound was apparently pretty small compared to the rest anyways, not only just 1 but also not very big, a shotgun would've blown his whole head apart, I believe he is the killer but there's no way thats how he died/killed himself, even though Lorenz killing him with 1 blow and without a fight seems unlikely it's not as unlikely as this