My picture of 'mental issues' needs to evolve apparently. I have no concept of a mental issue that has someone spending what they know are the last eight minutes of their life sitting in front of an open mic and not saying anything. I expect some sort of...for lack of a better term...crazy talk, or something. That takes 'hiding the mental issues' to a level I just can't handle.
Yeah the popular conception of a mentally ill person is someone who goes running around with a knife screaming their head off, but that's just one possible way mental illness can manifest. Imagine how many different types of physical illness - some more obvious than others, but just because a person seems physically alright doesn't mean they couldn't be weeks away from death due to a chronic illness, right? Something similar here, I guess. And, of course, severity of the illness can vary greatly. Someone with a bit of high cholesterol can still function normally for the most part, while someone with terminal stage cancer probably can't. As a personal example, I have a bit of mild depression, but I can and do still function normally for the most part (relatively). Someone who's constantly thinking of suicide or killing other people, on the other hand, probably not.
In short, mental illness covers a broad range of possible issues with varying symptoms and levels of severity, in contrast to the relative simplistic treatment of it we see in fiction and the media. Personally, I think it is quite an issue - this perception of mental illness - because it means a lot of people who are mentally ill don't realize they need help, because they think they're normal, they're not one of those crazy asylum serial killer loons. And sometimes, they might actually have really serious issues that don't manfest in obvious ways, and that's obviously a problem. Maybe if more folks knew about these sort of things we can prevent more tragedies like this.
Anyways, of course, it's hard for us to judge what exactly was this guy's issues given we don't have direct access to the evidence. News says he seemed normal and well-adjusted, but, well, the news says that sort of thing a lot.