A man is pushed out of a bus in downtown Las Vegas. Picture: Las Vegas Metropolitan Police/via Reuters

Las Vegas - It began as a verbal altercation on a bus, police said. Witnesses told authorities Cadesha Bishop was being "argumentative" during the ride, and a 74-year-old man, on his way off the bus, told her to be nice.

Video shows what happened next: Bishop shoved the man off the bus, Las Vegas Metropolitan Police said, through the open door. He landed face down on the sidewalk on top of his collapsed shopping cart.

The man, later identified as Serge Fournier, landed roughly "eight feet from the bus doorway" where he hit his head during the altercation in downtown Las Vegas on March 21, according to the arrest report. Although he refused medical attention at the scene, Fournier arrived at the University Medical Centre later that evening, police said.

Fournier died about a month later due to complications from trauma to the torso. On May 3, his family notified detectives of his death, at which point authorities ruled it a homicide.

Bishop, 25, was arrested and charged on May 6, in the death of Fournier. According to the Las Vegas Sun, Bishop was identified partly by a 'Love' emblem on her jacket and the Spider-Man backpack her son was carrying. He was allegedly present during the incident.

Police released security camera video of the incident on Monday, asking for more information from witnesses who happened to be there.

Bishop has been convicted twice of misdemeanour domestic battery charges in 2014 and 2015, according to court records. She is held on $100 000 bail with a preliminary hearing scheduled for Tuesday.

The Washington Post