Sucker punches are perhaps the most cowardly thing you will come across so this is never good to see at a boxing event.
On rare occasion they have even happened in the ring in boxing.
This one this weekend ringside involving fans:
Maybe the security could have been more proactive and diffused that before it even happened.
It appeared they were onto it straight away too and the guy who threw the sucker punch surely was the one who should have been ejected from the venue.
Not the other way round.
Unfortunately these things happen not just at boxing events but at all live sporting events on rare occasion when alcohol is involved.