My SIL was Marine Infantry. He’d be scary if he was evil. My son was Army Guard, construction. He’s a good shot, but only because he likes to shoot and practices. I was USAF. I had a chance to get some extra training from the Army and took it, but I wouldn’t be scary at all. The Army training I took emphasized teamwork and included things like grenades.
The shooter wasn’t actually very effective, given a target-rich environment, night, surprise and good body armor.
I'm glad my buddy found the Lord. He told me he used to enjoy hurting people and he's been into Brazilian JuJitsu for many years. I've seen him turn a he-man bodybuilder into a whining baby...so yeah I know exactly what you mean...lol