Died to land shark boss after I killed him???

I just finished killing the land shark boss and I was looking in my inventory to make room for the loot. Somehow I died after the boss had been dead for like 2 minutes with no other enemies in sight? I couldn't even tell wtf I died to... I guess it was something on the ground after it died??? Seriously, when the boss dies get rid of all the damage mechanics on the ground! This is so stupid and you know it. Now I lost hours of progress after I should have been safe. Actually so frustrating and I know nothing will be done about it.