Your projects started to go too far, you became too obsessed with it. It's starting to hurt the others... I'm sorry, I'll have to do it... I'm going to have to kill you!

So like... You are both scientists working in the same laboratory. You've been good friends in the past, but your experiments have started to go too far. Your last experiment exploded right in the laboratory, destroying many samples and injuring several other scientists. This cannot go on like this. But you apparently don't want to give up working on your projects... Well... It's your own fault for what is going to happen.