This handwriting is all over the fucking place. It starts out looking like a lefty wrote it.
Then, it looks like the paper was turned to compensate the lefty writing style without the slant. Then, it goes into the prison equivalent of "Yeah, my dick is big" with the "jumped by 16 dudes" portion, which looks like it was written by a righty.
Leads me to believe this shit is fake as fuck. Looks like someone is trying to mask their own loneliness by writing themselves letters, to me.