One Chicago Aviation Department security officer was put on leave on Monday   

United CEO has apologized for the incident amid mounting anger 

 An earlier Chicago Police statement claimed the victim 'fell' but has been retracted

New video shows the man bleeding heavily from the mouth after incident

The man was filmed screaming, then being knocked out by cops and dragged off the overbooked United flight at Chicago O'Hare on Sunday night

He was selected to give up his seat after no volunteers were found

Passengers had to give up their seats for United staff who were needed in Louisville, Kentucky 

Passengers were offered $800 to take a flight the next day  

The man claimed to be a doctor who had to see patients the next day