Suicide is a permanent solution to a temporary problem.
To most, they find living unbearable and some feel that they are a burden to their family. Even though it will shock the family and cause them pain and suffering, the suicidal person feels that will pass, eventually, and their family will go on. They just want and need their own pain to go away, and if medication or counseling has not helped them, then there is only one way out. The desire to end their suffering is so much greater than the knowledge that it will hurt so many people. It is very hard for most of us to understand suicidal people. In most cases, there is little or no warning, no signs that are so obvious they can't be overlooked. I have a suicidal family member. I watch for signs, but you cannot prevent it if they are determined. They will find a way. And some of them make several attempts which are caught in time, yet eventually they get it right. All I can do is pray and keep watching.
Hard truth to hear for most of us, I am sure, but it is what it is. It's pointless to say, "Oh, she was such a happy person, loved everybody, enjoyed life and lived it to the fullest... she would NEVER do such a thing!" We do not know the demons in other peoples' heads, and we are not meant to know, because if we did, we would hogtie our family member and never let them out of our sight. We cannot do that... we just have to be on guard. Sometimes the ones we think we know best... we do not know at all.