Police busted the cold-hearted creep who mugged an old lady in a Bronx elevator, authorities said Tuesday.

Homer Griffin, 50, followed the 81-year-old victim onto the elevator in the building at Grand Concourse and Marcy Place around 2:20 p.m. Friday, cops said.

Surveillance video shows Griffin acting as though he is going to help the elderly woman with her shopping cart.

But when she tried to leave, he pulled out a sharp object, cornered her and demanded money.

He snatched $200 from her purse and fled, cops said.

Police captured him after receiving a tip from someone in the community.

Griffin was charged with robbery, menacing and possession of a weapon.