(That's a nickname by the way)

Oh dear! Buttock doesn't look so good! Mwahahahahahahahahaha!!
You see, the entire group of members of the W.H.B (we hate Buttock) club ambushed him on his way home from school and beat him senseless. Bartek struggled to walk the rest of his way home but he'd had a very nasty blow to the head and before he could reach his front door, he suddenly spewed out a load of blood and snot, and then dropped dead.
The above photograph shows him in his last few seconds of life.