The pedestrian who was hit by a 272 bus in Shepherd's Bush on Monday was pushed, according to witnesses.
The man, aged between 40-45, suffered severe head injuries and is in a critical condition in Charing Cross Hospital after the incident at 3pm at the top of Shepherd's Bush Road.
Onlookers said the man had been pushed into the bus's path after a fight with another pedestrian. Police arrested and bailed a 28-year-old man until September shortly after the accident.
Ronan McNamara works at the Robertson, Smith and Kempson estate agents by the crash site and was on the phone a few metres down the road when the accident happened.
He said: "I heard a lot of shouting and roaring and then there was a crash. The guy wasn't moving whatsoever, he was just lying there by the pavement. The police and and ambulances got there within five minutes, and one officer told me the man's head had been crushed.
"They put him in a neck brace and took him away. They didn't seem to hopeful for him. The police seemed to know immediately what had happened and arrested a guy really quickly.
"There was a big crowd watching what was going on."
A worker at the nearby Ariana Cafe said another bus driver had come in and told staff the man had been pushed.
"The driver said the men had been fighting apparently," said the worker. "I saw a lot of commotion after the accident. There was a big crown watching and loads of police."
Paramedics were on the scene within minutes and took the victim to Charing Cross Hospital as a priority, where he remains in a serious condition.
Roads around the scene were shut off for more than two hours as police turned the accident spot into a crime scene.
The bus driver who collided with the man stopped at the scene and was not arrested.
