I think we all agree more details need to emerge before anything beyond sheer speculation can be made.

I do know, however, that as a general rule, we should be extremely cautious with any object that can inflict injury when interacting with police officers.  Tragedies have occurred when police have called out to a person, and in a split-second decision, shot that person when faced with a weapon.  Why?  Because there is an instinctive (or natural) tendency to respond to a command or verbal challenge by turning to face it.  If a person happens to be holding a gun, or in this case a crossbow, then the natural reaction is to turn to the source of the challenge while still holding whatever it is that's being held.

It happens in police-on-police shootings too.  After a notorious incident some years ago, it was advised that if you happen to be a black officer in plain clothes, that it would be unwise to engage in a foot pursuit holding your gun if uniformed officers may suddenly intervene.