I doubt suicide as they are having a Memorial for him. Last I checked they won't have memorials for suicide victims
I know of one elder's son who committed suicide and received a memorial at the hall. So it mustn't be a strict rule.
There's a lot of anecdotal evidence and statistics suggesting that Jehovah's Witnesses have a higher suicide rate than the general population, along with higher rates of depression and anxiety. So I think it depends on the circumstances and the victim's standing as a Jehovah's Witness at the time of death.
Does anyone know for sure whether there is a Jehovah's Witness rule to not host suicide victim memorials?