Suicide is a form of self control because one cannot control what is happening around externally, the external circumstances, and using suicide as a final form of control. It is extremely negative state of mind. Losing love, losing something, and cannot bounce back from a situation, one will generally get depression, from one depression to leads to another.
What I can give advise to in regards to people who are mentally unstable and thinking of suicide is to give some form of attentions to them, empathize with them, and generally speak your mind honestly about their circumstances but never touch about suicide. Be their friend, lend an ear, and push yourself to be a better person, and dedicate your prayers and thoughts to them. No matter how small is or fruitless your effort it may seem to be it might postponed their negativity and suicidal thoughts.
Is suicide associated with intent of killing, in this case, on oneself? Perhaps doing acts of saving lives, eg animal liberation, donating to a good animal cause will create merits for reducing negativity.