He wasn't really known as narcissistic, or even outgoing, but was 'diagnosed' as a psychopath.
https://extras.denverpost.com/bomb/bombp8.htm
“Oklahoma City brought him status. And the government he despised handed him the chance to prolong that status when, just days before his original May 16 execution date, the FBI disclosed newly discovered documents that had never been turned over to defense attorneys.
The foul-up gave McVeigh another 25 days of life and brought him yet more attention.
It played into what the prosecution psychologist said was “a combination of [McVeigh’s] narcissism and boredom, and there may be certain grandiose fantasies too.”
“In the narcissism there is a sense of being a legend in one’s own mind,” said the psychologist, who asked that his name be withheld because of his work for the government. “There’s an inflation of one’s self and one’s importance, and sometimes there’s even a sense of immortality, that somehow your execution or death is not real. It becomes so pervaded with grandiosity that, instead of being frightened of death, it’s embraced.
“And he was a sensation seeker. To the max. And being in prison, particularly in general isolation, it’s just exceedingly boring. Particularly if you’re drawn to sensation. He would be deeply bored, enough to feel it consciously day in and day out.”
