Riverdale police on Friday asked for the public's help in finding the person believed to have sexually assaulted four girls since late July and as recently as last weekend.

The victims ranged in age between 14 and 16, and most were attacked in the early-morning hours, said Riverdale Police Chief Pete Satriano.

The male offender is described as black, between 5 foot 9 and 6 foot, with a medium build and possibly wearing his hair in a braided style, Satriano said. The offender's age is unknown, he said.