Dallas Sheriff's Department spokeswoman Carmen Castro told The Dallas Morning News Brown was arrested Wednesday night and "released over to the FBI" in the morning.
"There's nothing listed on his profile for any offenses," Castro told the newspaper Thursday. "I've tried to reach the FBI myself, and they said they don't have anything to share." The FBI's local spokesperson also declined to comment to the News.
California law firm Leiderman Devine said on Twitter Brown was arrested for threatening an FBI agent.
Wired's Threat Level blog said Brown "posted a long and rambling YouTube video in which he talks ... about retaliating against an FBI Agent named Robert Smith after he learned that his mother might be hit with obstruction-of-justice charges for an incident related to a laptop belonging to Brown that he apparently hid."
"Robert Smith's life is over," Brown says in the video. "So when I say life is over, I don't say I'm going to kill him. But I'm going to ruin his life and look into his [expletive] kids because Aaron Barr did the same thing and he didn't get raided for it. How do you like them apples?"
Barr is a former chief executive officer of HBGary Federal whose email account was hacked by Anonymous in February.
"Any armed officials of the U.S. government, particularly the FBI, will be regarded as potential Zeta assassin squads and ... they know that I'm armed ... and I will shoot all of them and kill them if they come and do anything because they are engaged in a criminal conspiracy and I have reason to fear for my life, not just from the zetas but from the U.S. government," Brown says in the video.
Brown has claimed responsibility for cyberattacks on the Church of Scientology, Visa and MasterCard, the News said.