The armed geezer who shot up a posh Madison Avenue men’s store and then went on a bizarre interstate crime spree was killed after he crashed into a parked car during a police chase in Maryland, authorities said yesterday.

Arthur Williams lugged his oxygen tank into Sarar, on Madison Avenue near 46th Street, on July 9 and opened fire inside the swanky suit shop, police and sources said.

The geriatric gunman, believed to be in his 70s, fled in a shiny black Cadillac with Alabama plates, and continued his one-man crime wave by hitting two hotels in Maryland early Sunday morning, authorities said.

He then led cops on a 2½-mile chase before veering off the road and fatally crashing into another car in Clear Spring, authorities said. He was pronounced dead at the scene.

The NYPD had released a video of the robbery early yesterday, which prompted the man’s nephew to inform them of his death.