A thief who stalked her victim on Muni's light rail system was arrested Monday night, shortly after she swiped a fellow passenger's laptop.

The victim, a 25-year-old woman, says the noticed a 30-year-old woman "behind her the whole time" as the two rode a Muni Metro train down King Street at 10:20 p.m. Monday.

When the younger woman got off the train at Fifth and King Streets, the elder woman followed. Approaching the victim, the suspect said that she had a gun, as she held her hand in her purse and pointed the firearm at the victim.

The suspect then grabbed the victim's bag, "threw it on the ground and stole the laptop," according to the San Francisco Police Department.

The laptop thief fled on foot, police say, but was caught and arrested by police near the scene. According to the SFPD, the laptop was recovered, and will be returned to its rightful owner.