killing boss underground

not sure where to post this one because i don't know if is hack or glitch...player name Ryzen1800X, from family AMD if im right, was killing bosses from the scroll underground and very fast. (watch in HD-Name is visible on minimap 0:17sec mark)
here is the link for you to jugge;

 

It just a known bug usually happens if you summon boss while you are in a party ,or if you summon boss and gets disconnected then you find yourself killing bosses underground if you are lucky to reach the boss. Sometimes you have to wait for server restart to fix the problem...

One more thing, while someone is summoning bosses he disappears from other peoples sight so he don't get pked/ksed. You will only see the players on your mini map, plus you can't kill someone else's boss.

 

Thx for info.....