[quote=@Saint Girralo]
That didn't answer my question, Does Doom Guy need to MAKE THE KILL for the power-up to have a chance of showing up or can ANYONE MAKE THE KILL?
[/quote]

*Rubs sinuses*

It's [u]anything that dies within fifty feet of him[/u]. It doesn't matter who kills what. It's about who dies and how close they are to Doomguy. 

Wait, let me change tac. 

NO. IT CAN BE ANYONE. SO LONG AS SOMEONE KILLS SOMEONE ELSE WITHIN CLOSE PROXIMITY TO DOOMGUY THERE IS A CHANCE THAT THE PERSON WHO JUST DIED MIGHT TURN INTO A POWER UP. THIS POWER UP CAN THEN BE ACTIVATED BY ANYONE WHO TOUCHES IT. 

Really, guys, it's a small little gimmick - try not to get so focused on it :)