During De Rossi's fight with the man at Kellie's uncle's house, he shoots the man twice, with two blood stains appearing appearing on the man's chest.
But when the FBI agents are examining the scene, Agent Ortiz states that there is one shot to the chest.
Kenny flashes his badge at the NYPD detective and tells him the FBI is taking over the investigation of his friend's assault. That is not something that would really happen, the law is very clear about what federal law enforcement agencies do and do not have jurisdiction over. The FBI cannot just take over whatever criminal investigation they want.