The irritating phenomenon of Muni bus bunching — in which multiple buses run right behind one another, instead of evenly spread out the way riders might prefer — both helped and hurt an alleged mugger Tuesday night, when police say that he reportedly robbed passengers on one bus before getting nabbed on the following one.

According to San Francisco Police Department spokesperson Officer Grace Gatpandan, Derrick Woods, a 19-year-old San Francisco resident, hopped on Muni's 9-San Bruno bus near 16th Street and Potrero Avenue at 7:25 Tuesday night.

Once on the bus, Woods took a seat across from a 21-year-old man, then tried to wrest the man's cell phone from his grasp. When the phone owner resisted, Woods pulled out a semi-automatic handgun, and the phone owner complied with the robbery.

Woods then turned his attention to a 17-year-old girl, Gatpandan says, demanding her phone at gunpoint. She, too, complied.

After the two thefts, Woods got off that bus, and onto one that was following right behind the scenes of his alleged crimes. That's where police found him, Gatpandan says, riding along with the gun and the stolen cellphones on his person.

Woods, was arrested and booked into San Francisco County Jail. He faces two counts of robbery and multiple gun charges related to his allegedly carrying a concealed, loaded firearm that was not registered to him with the intent to commit a felony.

Perhaps also of interest: Suspects In Bayview Shooting Flee On Muni Bus