Late in the thead but I have seen the words "decision" and "thinking" regarding suicide here and elsewhere. From what I know the mental state before suicide is pretty distorted and irrational, forms of psychosis and psychotic depression. So there ain't a lot to work with in terms of making a decision.
The time to take action is long before, when one feels bad but not that bad yet. It's a pride thing, people tend to be afraid to ask for help, seeing that as weak. Just the opposite is true, revealing faults and weaknesses is a sign of strenghth and confidence.
From what I understand Williams was under great financial pressure, which is a common predicate to depression and suicide along with romantic problems, career problems. So those problems are the warning signs for many of us.