A woman was sexually assaulted July 4 in a parking garage at Ballston Mall, Arlington police said.

The woman, 23, had been shopping at the mall and was walking to her car at 2:30 p.m. when a man grabbed her from behind, said Dustin Sternbeck, a police spokesman. The man lifted her skirt and sexually assaulted her with his hand, Sternbeck said.

The woman screamed and the man went to a nearby stairwell and ran off. The victim got in her car, left the garage and called police, Sternbeck said.

This is the second sex assault of a 23-year-old Arlington resident reported in the county in recent days. Tuesday night, a jogger was assaulted at knifepoint near mile marker 44 on the Four Mile Run bike trail.

Police do not believe the attacks were carried out by the same man. The attacker with the knife was described as a 5-foot-6 Hispanic man, while the attacker in the parking garage was described as African American and 6 feet tall.