The one thing that is clear is why he used a suppressed weapon. He did not want to call any more attention to the incident than necessary. Ideally, he would have killed the CEO and walked away unnoticed. The suppressed pistol he used is an NFA weapon and very few people on earth have purchased one. This will likely be his downfall.

When silencing a Browning type tilting breech handgun, a silencer will cause the weapon to malfunction with most every shot unless you have also added a booster between the suppressor and the pistol. (more on that in another blog)

The assassin in New York was using a bizarre bolt action 9mm pistol. It was not jamming between shots; the was assassin was working the bolt on the pistol. The pistol is an NFA item; it is called a B&T VP9. Since this was an NFA weapon, the assassin should be caught in very short order. Above is what the bolt action suppressed pistol looks like. It has a standard magazine. To function the weapon, you push the bolt forward and twist to lock it before shooting. To unlock, twist the knurled knob and extract and eject.

EDIT: It was a ghost gun likely on readily available parts. He likely completed the weapon with a 3-D printer. Luigi Mangione, an Ivy League grad and person of interest was arrested with the 3-D printed weapon and suppressor. It had nothing to do with a B&T VP9.