The lesson? Always wear protective head gear, too. Or, you know, just don't box unsupervised.
Sorta related: during my senior year of college, in the middle of fraternity rush, we thought it would be a swell idea to have two guys in the fraternity (who also happened to be 5-0, 120-pound wrestlers) box each other because ... well, we were all idiots.
A huge crowd gathered, the two pugilists went at it (let's call them Buster and Mike), everybody was having a grand old time ... right up until the moment that Buster knocked Mike out. Cold. An "Oh, God, he might be dead" silence fell over the room before he hit the concrete floor. Wisely, some guys quickly loaded Mike into the car and took him to the emergency room.
I found out later that everything was fine -- Mike didn't even suffer a concussion -- except that somebody accidentally slammed the car door on his ankle as they were taking him to the hospital. He limped noticeably for the rest of the week. Good times.
video via Off the Bench