A loss like this is always tragic. There was a very popular song back in the 80's called, "Don't Know What You Got till it's Gone". It's true. Most of us really have no idea how good we've got it until it's taken away from us. You are now realizing that fact.
On a more practical note, I hope you have learned a valuable lesson here. You're only 19 years old, and have several decades ahead of you, so listen very carefully. When someone tells you that they are considering suicide, take them at their word, they're completely serious. People tend to be dismissive of the subject of the taking of one's own life, generally because it makes the listener uncomfortable.
As a hospice chaplain I hear this topic discussed quite often, and I've learned one universal truth: Any and every threat of suicide is completely valid. You are learning this now because you may need this experience later. The next time you hear someone talk like that, you'll be ready. Good luck.