The shooting happened about 5:45 p.m. near the intersection of Pecos Road and Washington Avenue, Metropolitan Police Department spokeswoman Laura Meltzer said.
Jonathan Potter, 20, was shot inside the bus and taken to University Medical Center, where he died.
Witnesses told police there had been an argument on the bus between Potter and three others. The group of three was getting off the bus near Pecos and Washington when one of them, believed to be between 15 and 17 years old, leaned back and fired the fatal round.
The teen was black, about 5 feet 2 inches tall with a slim build. He fled the bus with the two others — black men believed to be between 18 and 20 years old.
One of the men was about 5 feet 9 inches tall with a medium build and a goatee, last seen wearing a black beanie and a black sweater.
The second man was also about 5 feet 9 inches tall with a lighter complexion and a tattoo of roses with an unknown name on his upper left chest. He was last seen wearing a red sweatsuit and red shoes.
Before the shooting, the bus was headed west on Washington, between Nellis Boulevard and Pecos. Detectives urge anyone who may have been a passenger on this bus between 5:30 and 5:45 p.m. Thursday to call investigators at 702-828-3521 if they have not already been interviewed.
This was the 161st homicide within Metro’s jurisdiction this year.
Contact Rachel Crosby at firstname.lastname@example.org or 702-387-5290. Follow @rachelacrosby on Twitter.