Being a combat sports referee is not an easy job and is subject to intense scrutiny on a regular basis (especially from us as fans). With that said, there is literally nothing defensible about what happened at this amateur MMA event in Brazil.
Referee Kleber Lopes was the third man in the cage for a 198-pound match between Jessian Lucas and Michael Douglas (definitely not the actor). The modified rule for this card was that strikes to the head of a grounded opponent are not allowed. Keep that in mind when you see footage of Douglas planting Lucas with a head kick.