1) Metro Dade Narc officer in the early 80s used a MAC .380 SMG and suppressor to kill a CI. He "borrowed/stole" the firearm from his friend whom was the Transferee.
2) In a domestic dispute in PA, a cop killed his wife with a short barreled shotgun (SBS) in which he was the transferee.
In the mid 90s, a SWAT officer used an HK MP5SDA2 that was form 10'd to his department to kill his wife, another cop (his wife's boyfriend), the IA detective, and his supervisor.
4) An officer used a suppressed .22 LR that was registered to him to kill his wife and lover when he came home from work early. He used his own .22 Ruger suppressed as he was a SWAT team leader who took his own pistol on patrol to take out street lights to darken areas before a SWAT raid.
5) A Destructive Device was used by an AR doctor to bomb someone on the medical board who suspended his license.
In TULSA, a cop killed his (ex?)wife with a crossbow. Very quiet. The only noise was her screaming when she saw a short feathered shaft sticking out of her chest.
No registration needed.
As for title three weapons, remember at the funeral of a cop when his supervisor said he was tired of going to cop’s funerals who were killed with Uzis!
A quick check showed NO cops killed with full auto Uzis in the USA.