Looked at a bit of the video. Overhand right, overhand right, overhand right. Nobody in that ring knew how to fight.
Very sorry to hear what happened. This is to agree with mber's statement that anything can happen. It also highlights a few other lessons:
1) As mentioned in a thread on preparing to defend yourself in a 'street attack', not that neither party defended; they only attacked. Common. Every slow, sloppy, looping, telegraphed overhand right landed or missed entirely; no blocks. Learn to freaking block.
2) Those who are quick to engage in mutual combat on the street and think no ill will come of it; if this fight had taken place outside the ring and in the US, chances are good the 'winning' fighter would be facing criminal charges today, if not actual manslaughter charges. Because you're responsible for what happens to the person you punch; even if they fall and hit their head on the pavement, that's on you if you're not engaging in legitimate self-defense.