The FBI became involved because a firearm was used in the homicide James Patrick Deleon Guerrero.
The Department of Public Safety Commissioner says the autopsy showed that Deleon Guerrero died of a gunshot wound to the right side of his chest.
The late security guard is the police chief's cousin.
Deleon Guerrero was on duty at Royal Poker in Afetnas Tuesday last week when a masked man entered and shot him with a handgun.
Sources say police are pursuing "good leads" on the identity of the masked gunman.