Do you guys know what really happend to james forrestal?

He was involved in the alien cover up, and I know he had a nervous breakdown before he died. It had something to do with the aliens, but what scared him that bad that he had a nervous breakdown? I think its more than the fact that they exists, is it simething thats to take place in the future? Like an invasion or something? Why would they kill him for trying to release the truth? That could mean there not friendly right? Why else would he have a mental breakdown? Plz guys no immature answers. Thanks