According to Times Online, Gunn was incarcerated after he ordered executions during his tenure as a mob boss in a criminal empire so dangerous it helped earn Nottingham the nickname "Assassination City."
He says that the folks overseeing the prison allowed him to set up a Facebook account after he claimed it was a basic right. The prison denies this. Either way, he has since used the account to threaten enemies.
For example, he posted a status update promising that he would soon return to the streets: "Some of you will be in for a good slagging, some have let me down badly, and will be named and shamed, f****** rats." It's not known whether or not he used private messages or other tools to contact people in his crime ring. Once the media caught on to what Gunn was doing, authorities killed his Facebook page.