[calyth2018]

Not that professional. Looks like a suppressor on a pistol, but not configured and tested so that it doesn't malfunction. Shooter is skilled enough to deal with the malfunctions.

This suggests that shooter's at the minimum enthusiast, possibly trained for a different profession as a rank and file guy, but not enough to actually put somewhat specialty gear together reliably.

I don't think the guy's a hired assassin per se, but more likely a very disgruntled person who felt wronged by UnitedHealth.