Police said they learned of the plot when an officer responded to a burglary at Cash America Pawn early Saturday morning and arrested Antonio Thomas in the store, Debadie said.
Police said Thomas, 17, had one handgun and one airsoft BB gun, and told investigators he and three others stole firearms and were also seeking bullets to shoot police officers, the chief said.
Surveillance video showed the suspects using a ladder to climb to the roof to break into the building, police said.
Thomas was accused of burglary and theft of a firearm and booked into parish prison.
Since Saturday, detectives have arrested two other suspects in the case, including a 13-year-old boy. A fourth suspect possibly remains at large, police said.
