Caleb McGillivary was rushed from the Union County jail in New Jersey to a hospital with self-inflicted, non-life threatening injuries on Wednesday.
Union County spokesman Sebastian D'Elia tells The Star-Ledger of Newark the 24-year-old was later taken to another health care facility and is under guard.
D'Elia, citing privacy issues, declined to give details about the injuries.
The Canadian is held on $3 million bail, charged in the May 12 beating of 73-year-old lawyer Joseph Galfy Jr. of Clark.
McGillivary gained a measure of online fame in February after intervening in an attack on a California utility worker in which he described using a hatchet to fend off a further attack.
Information from: The (Newark, N.J.) Star-Ledger