Airbubba: I have since discovered that Chicago PD are not quite telling the whole story. After being knocked about and dragged off the aircraft, the passenger ran back on board where he was filmed by a fellow passenger, bleeding profusely from the mouth. The fellow passenger reported that eventually the man was removed from the aircraft, again, but this time on a stretcher.
The sad thing is that, when the airline began asking for volunteers to disembark, this man and his wife had offered to give up their seats. Until United told them they would not be able to fly out of Chicago until 14:30 the following day. That was when the passenger withdrew his offer, saying how he needed to be in Louisville to see patients the next morning.