A Brooklyn man wanted in January’s brazen robbery of the Midtown Cartier store freaked out and grabbed a gun when a FedEx man rang his buzzer — then accidentally blew his own brains out trying to hide under a couch, sources said Thursday.

Ralik Hansen, 28, believed that the driver, who rang every bell at 360 Snediker Ave. in Brownsville to deliver a package on Oct. 31, was a cop, authorities said.

“In his paranoia, he ran to the bathroom and grabbed a .357 and was trying to shimmy under his couch to hide in his apartment when the gun went off,” a law-enforcement source said.

“Hansen erroneously thought it was the police coming to get him,” added Leon Krolikowski, the police chief in New Canaan, Conn., where Hansen and his crew allegedly hit a jewelry store a year ago.

Hansen had faced possible life behind bars on robbery and weapons charges, authorities said.

He was part of a crew that entered the crowded Fifth Avenue store at 12:30 p.m. on Jan. 31 and used hammers to smash open display cases, police say. They stole 16 watches worth a total $709,000.

Hansen was indicted in April. Four other suspects are in custody, and the FBI on Thursday identified two more — Courtney Hardin and Jamal Dehoyos.

They are wanted in heists at Litan Jewelers in Brooklyn, the Atlantic City’s Borgata Casino, and jewelry shops in Richmond, Va., and Cranford, NJ.