Peter Lance's Deal With The Devil goes into some detail there.

Farace killed one heck of an illustrious decorated/educated/veteran officer of the law and US soldier named Everett Hatcher.

After the killing, even Gregory Scarpa Sr. disowned him, publicly, in a newspaper interview. Scarpa was his uncle.

The way the killing of the DEA agent transpired is suspicious to me because he was doing a sting operation being tailed by his co-agents when for some reason, the tail was lost and Farace was able to shoot Hatcher in relative privacy. I found that strange.

Now that you know the name of the agent he killed, it should be easy for you to look up how long it took that murder to catch up with Farace.

I did not yet see the movie you referred to.