Police have arrested a man they say was behind a string of robberies in Manhattan.

Police say 65-year-old Frank Peterson carried out eight robberies since October.

The latest happened Monday at a building near 127th Street and 5th Avenue in East Harlem, according to police.

Police say Peterson approached a 78-year-old woman from behind as she was checking her mailbox.

They say he then put a knife to her throat and took two rings and cash before running away.

Police say the other robberies took place in Morningside Heights and the Upper East Side. They say all of the victims were women. 

Peterson has been charged with robbery and burglary.