A Big Apple cop assisting US Marshals with an operation in Jersey City accidentally shot a federal agent in the foot while trying to kill a dog that was attacking him, law enforcement sources said.

The team of federal agents and local cops showed up to a home on Bayview Ave. on Thursday morning to serve an arrest warrant to Javan Reaves, 25.

When they entered the home, a dog pounced on one of the agents and started biting him, sources said.

The NYPD officer then took aim and shot the dog, killing it, but accidentally striking the marshal’s foot in the process.

The marshal was not seriously injured.

It’s not immediately clear why authorities showed up to arrest Reaves.