How do people commit suicide?

We were playing, a friend and I, fighting hordes in Warehouse Sewers, when suddenly...

I swear he's not suicidal at all (even if he's playing a gloomy Shadow). We didn't understand what happened. Any idea ?

There are flask mods that reduce your health (i.e by 15%) on use. Take it with low health and you suicide.

Any skill or affix that will lower your life under 0 will cause you to "suicide" yourself. Some examples:

• Blood Rage (green gem) (-4% life per second)
• Blood Magic (red support gem) (spend life instead of mana for linked skills) (will not activate skill if hp is to low)
• Blood Magic (passive skill) (spend life instead of mana for every skill)
• Flasks' Caustic mod (- X% of mana recovery from life on use)