Troopers found 4 shell casings at the shooting scene at the barracks. They then found his jeep stuck in a retention pool in the woods where he was driving through a path to get away after the shooting. There were casings in the jeep that matched those at the scene along with his I.D. The jeep was also registered to his parents. When troopers searched the parents house where Frein also lived, they found more casings in the garage. All three sets of casings show the same toolmarks so they know they were all shot from the same weapon.
Well, one may deduce....he’s not the brightest bulb in the package.