I will add, sorry, no local police officer would or could ever know if someone is in the witness protection program, Even state police will not know, There is nothing in their new ID that will ever tell something.
Some officer was either lying to you or messing with you for some reason.
Only the Federal Marshal service ( and not all of them) will know who witness protection people are ( in the federal program)
So no this man is not in the witness protection program, because if he was and anyone knew, their life would be worthless, and marked for death,
If he was in the "mob" before, he is hiding from them and for him to do anything to bring attention would bring death to him.
If he told the officers that, he was just lying to them to sound big.
File a police report against him. if the police will not do anything, go to the DA.
But also just don't answer the phone if he calls.