Fournier then appears to fall on his walker, landing on his head in the process.
Bishop was transported to the Clark County Detention Center where she will be charged for murder.
The surveillance video shows Bishop allegedly push Fournier out of the door of the stopped bus.
The Clark County Coroner's Office ruled Fournier's death a homicide after an autopsy showed he died from complications ti blunt-force torso injuries.
Cadesha Bishop was arrested and charged with open murder of an elderly-vulnerable person.
Witnesses say Bishop pushed the man out of the bus door after getting into an argument with the victim and other passengers.
Later that evening, Fournier took himself to a hospital for his injuries. She is held on $100,000 bail with a preliminary hearing scheduled Tuesday. "Very nice, religious person", he added.
Trevor Taylor, a neighbour to Mr Fournier, said: "No matter what his age, she should not have done that. People need a little more patience than what they have these days".
He leaves behind a wife who is disabled, according to KSNV. "'God bless you, ' and that was the last thing he said to me".
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. Police said she was seen in the security video, which has yet to be released, walking away holding the boy's hand.
Bishop was previously convicted twice in 2012 and 2013 of domestic violence misdemeanors.