Super sad, this wasn't a hijack it was a troubled soul. Don't think he wanted to hurt anyone and it's sad that he wasn't able to get the help he needed. Kudos to air traffic services and the pilots on the frequency for being so professional to the man. I hope they don't have too much guilt to bear.
Also, I hope the FAA or any authoritative governing body doesn't implement some radical change to American laws. This is a one in a billion event, and having security made stricter will make it even more difficult for those in the aviation industry. New onerous policies and procedures that might help prevent it in the future while tripling the time it takes to do some task and increasing headaches for everyone.
Quick thought, from my perspective in the aviation industry. Anybody in the aviation industry, pilot or not, such as this mechanic, would have to undergo medicals. Perhaps he didn't seek mental help due to the fact that the aviation industry has draconian regulations with ANY form of assistance. The possibility of a failed medical would mean the loss of a career and hence income, even if he was just a mechanic.