Having your bike stolen is an unpleasant San Francisco rite of passage, like stepping in feces of undetermined origin or having the 5 Fulton pass you by as you wait at the bus stop. But typically, those thefts happen when you leave your bike locked up at a rack, then someone like this guy shows up. But if you have your bike with you, grasped in your hands, it should be safe, right? Unfortunately, based on two crimes in the last 24 hours, wrong.

For example, it was noon Tuesday in the area of Pier 28, the Embarcadero-adjacent Pier you see as you're headed to the Hi-Dive. According to the San Francisco Police Department, a 19-year-old man was "standing next to his bicycle" when they say a man described as around 35 years of age "got on it and attempted to ride away."

When the bike's owner tried to stop the man from taking it, the suspect knocked the victim "to the ground," police say, then "fled on [the] bicycle in an unknown direction." As of Wednesday morning, police say that the thief remains at large.

Moving the clock forward by nearly 12 hours, and a second brazen bike heist occurred, this one at Seventh and Market Streets.

At 11:30 p.m. Tuesday, police say that a 17-year-old male bike rider was approached by a 24-year-old man who "showed a handgun hidden in his waistband" and demanded the teen's bike.

"Out of fear," police say, the kid handed over the bike and the suspect took off. But this story has a slightly happier ending, as shortly after that, according to the SFPD, officers caught sight of the suspect. He was arrested, police say, for the theft of the bicycle and was booked into San Francisco County Jail.

Previously: Video: Thief Steals Bike On Valencia In Broad Daylight