Arpaio says Simpson quit his job last week at a Bath auto repair shop and was later pulled over by police as he was leaving town.
The sheriff said investigators don’t know whether Simpson was intending to carry out his threats, but he said items found in Simpson’s vehicle were disturbing. Authorities found several weapons, zip ties and a news clipping about last December’s mass shooting in Newtown, Conn.
It wasn’t immediately clear why Arpaio’s office had jurisdiction to arrest Simpson in New York.
Simpson is expected to be brought to Arizona on Wednesday, Arpaio said. Court records show he does not yet have a lawyer.
Earlier this year, a Maricopa County jury convicted Arias of murder in the death of her boyfriend Travis Alexander, but the jury later deadlocked at the sentencing phase of her trial.
A new jury could be impaneled to decide sometime in late September whether Arias should be sentenced to death or life in prison.