LOWER EAST SIDE, Manhattan — A 55-year-old man was on his way home work when he was attacked from behind in the lobby of his Lower East Side apartment building.

Two men followed him into the building around 10:30 p.m. Monday night, police said. One of them punched him and the other struck him repeatedly with a heavy, metal object.

The man was knocked to the floor of the lobby. He blacked out and doesn't remember what happened, but surveillance footage shows the story.

His attackers took his shopping bag full of groceries and fled northbound on Pike Street toward Madison Street.

Officers were back at the scene Tuesday putting flyers up warning people who live there to be on the look out.

Police have asked for help identifying the attackers. One of the men has facial hair and was last seen wearing glasses, a black hooded jacket and a black hooded sweatshirt. The other attacker was last seen wearing a black baseball hat, a black jacket, blue jeans and tan boots.

Submit tips to police by calling Crime Stoppers at 1-800-577-TIPS (8477), visiting http://www.nypdcrimestoppers.com, or texting 274637 (CRIMES) then entering TIP577. Spanish-speaking callers are asked to dial 1-888-57-PISTA (74782).