No one can say for certain that suicide is an automatic "go to hell" or not. It is not directly addressed in scripture and nothing (in context) says the person goes to hell no matter what. People have their opinions and some use fear and scripture to back up their claims so they can "know for certain" and scare anyone else away from trying to commit suicide.
What I see in scripture is that our Father and Jesus are not looking for relationship with us based on fear. They are looking for relationship with us based upon a love for us that we cannot imagine and does not change. Having committed a sin and then dying without having a chance to repent does not mean you lose your salvation and go right to hell. That is not consistent with a God of Love and compassion, that is a God based on fear to keep his subjects in line and doing what it wants. God loves us and calls us sons and daughters, not subjects. He does not look on us with disdain because we have done something wrong, he looks on us with compassion. Remember the people Jesus healed, the woman at the well, and the woman caught in adultery? He does not beat us down because we sin, Jesus lifts us up out of it. We all have sins in our lives and there is no "degree of sin." Sin is sin.
The thought that it's an automatic go to hell is a blatant fear tactic and is not consistent with scripture or Gods law of love. To say that you go to hell because your last act was to kill someone is absurd. Your salvation is not based on whether or not you follow every letter of the law or live a perfect life. In this way of thinking, if you are the cause of a car crash that causes someone else to die and you die as well then you automatically go to hell because your actions killed someone and you never repented of it. It would also mean that every soldier who died in battle went to hell because they were in battle and killed someone and they were killed before they could repent. Someone could also avoid the automatic go to hell because they could take an overdose and repent then die. See, the logic is flawed and there is no God of love or compassion in this scenario. It's based on man's fear mongering. It's also the same cult-like theology that says if you die before you're baptized you go right to hell. You can be on your way to the baptism ceremony but you died on the way so you're now in hell. Christianity has blatantly said that is not the case, yet the same logic is used for the "go right to hell if you commit suicide" principle because we obviously don’t want people to commit suicide.
As for suicide causing someone to be classified as a murderer in context with the scriptures, I do not see it. Doing something once does not define the person. It may be something someone did one time, but that does not make it their identity. Jesus said that everyone who looks on a woman lustfully in their heart has committed adultery. If that's the case then every guy on the planet will go directly to hell because they are an adulterer. The same thing where Jesus said anyone who hates his brother is guilty of murder. Again, everyone on the planet has inherited a direct ticket to hell as a murderer. The difference of being a "murderer, adulterer, thief, drunkard, etc" is a lifestyle characterized by these things and having a heart hardened to the Lord. Again, doing something once does not define the person or their heart.
Does God condone suicide? No, obviously not. At the same time, God knows our beginning and our end. He is not taken by surprise and knocked from his throne because someone commits suicide. He knew before the person was born that they were going to do that or not do that. It's already accounted for in His plan. He knows what choice any of us will make. For me, I've been on the brink many many times and have not gone through with it for different reasons. My reasons, among other things, are the hurt and pain it would cause my family and friends. When I get that low, I am sorely reminded that God is hurting with me. Scripture says he rejoices with us and he hurts with us. God is not fickle. If I were to make the choice of suicide in a weak moment, God's character would not change from a loving and compassionate God to an angry vengeful one throwing me in hell forever. No, I would die and go to heaven where I would be welcomed by the Loving Father and his Son Jesus. If I chose my timing rather than God's timing to die He already knows it. I would "pay for it" by not getting to see my future play out as God had intended. He knew I would die then, but his perfect plan for me was different. I believe I would "pay for it" because I would be grieved as He would at the missed opportunities.
Going to heaven or hell is based on one thing only...whether you have accepted Jesus and made him Lord of your life. If you have, regardless of your "final act in life," you will go to heaven.