The incident happened around 8 p.m. Wednesday near Wilshire Avenue and Vermont Boulevard.
"I started filming it for my husband who doesn't realize all the crazy stuff that happens on the bus all the time, and then it got really intense," said Erica Rodriguez, who captured the incident on camera.
Rodriguez says she's not really surprised that no one stepped in to help the man.
"It was definitely scary. I mean, you hear about people on buses with guns all the time in L.A. and it was concerning, but luckily, that didn't happen," said Rodriguez.
The bus finally stopped and most riders got off. Los Angeles County sheriff's deputies say they did get a call about the incident, but say the man was gone by the time they arrived.