A church-going grandmother waiting at a bus stop in Williamsburg had her legs mangled after a livery-cab driver jumped the curb and smashed into her early this morning, authoriites said.

The 20-year-old driver, Maximo Espinal Jr., fled the scene after the 5:15 a.m. crash but turned himself into police about five hours later, officials said. His license plate was found in the street, still attached to his car bumper, which had fallen off from the impact.

He was charged with leaving the scene of an accident with injuries and with reckless driving.

His victim, Debra Munize, 58, had both her legs injured, friends and witnesses said. She was headed to church at the time, friends said.

Local resident Fernando Sanchez, 19, said he helped wrap her in towels while his mother called 911. He said Munize was screaming and spoke about her granddaughter to stay calm.