Just so depressingly sad to know that they most likely killed this kid because they were too scared to face the music of beating him.  They likely believed they could kill him and get away with that over dealing with the consequences of their actions.  Why else would they logically (or rather rashly) think to kill someone?  I highly doubt it was because he simply "smoked all the weed"  That was likely why they beat him.  

After beating him they must have thought "oh god we will get in trouble, how do we cover this up.  yes lets kill him instead".  :(  Horrible just freaking horrible!