Welcome to Just Answer and thanks for your question.
There are several ways you can look for information, but none of them is guaranteed to yield results. You can check the local newspaper archives to see if there is information prior to his death. This would include things like automobile and other types of accidents, murder, etc. You would also check their archives for an obituary, but it sounds like you have already tried that.
Death certificates list a cause of death, if this is what you are specifically looking for. However, most countries and states will not allow anyone other than a close family member or an attorney representing the family to obtain a complete death record that lists the cause of death. Just about anyone can get a death certificate with that information redacted, but not the complete record.
If cause of death is what you are looking for, and it isn't in the obituary or in a newspaper story, the only other option is asking a family member or other close friends of the deceased.
Please let me know if you have questions.