People are saying he was "unhinged" or mentally ill, but it sounds like he was simply sucked into an online scam. That happens to normal people all the time (even professionals through "whaling"). If you believe your scammer, and he tells you about freeing hostages, and those stories corroborate with what you hear on the news, then what normal person wouldn't get agitated and emotional? That doesn't sound like mental illness, it sounds like normal reaction to finding out that the one person who could save some hostages is refusing to cooperate. Don't forget his friend was actually killed in Afghanistan so he's got some genuine emotional connection to these troubles already, making the other stories easier to believe perhaps.

What would you do if you believed you had a way to free a hostage and the FBI just told you to get some sleep? When the hostage was killed, what would you say to that FBI worker? Normal mentally healthy people would get angry and obsessive when they believe they're being impeded from saving lives. I've seen more extreme reactions for far lesser problems.