We often think people will only die by suicide after a long history if depression. Some suicides happen very quickly, one study that asked suicide attempt survivors how long was there between you thinking about suicide and carrying it out, 24% said five minutes or less so it is often an impulsive act. We know poor sleep makes people far more vulnerable to making poor decisions.
Simon, T. R., Swann, A. C., Powell, K. E., Potter, L. B., Kresnow, M. J., & O’Carroll, P. W. (2001). “Characteristics of impulsive suicide attempts and attempters.” Suicide and Life-Threatening Behavior, 32(Supplement to Issue 1), 49-59.