Authorities in Rhode Island are investigating after two anonymous letters were sent from a correctional facility threatening to kill three officers and other staff.
Richard Ferruccio, president of the Correction Officers Union, says the letters were found Monday afternoon.
They were sent through the interdepartmental mail system at the medium security facility at the Adult Correctional Institute in Cranston.
Ferruccio says the first letter made specific threats against three officers, included their home addresses and vehicle descriptions and was signed "ISIS."
He says the second letter that was sent out made threats against a lieutenant and another staff member.
A spokesman from the ACI told WJAR-TV the inmate- or inmates -wrote the letter because they felt mistreated.
Ferruccio says the ACI and state police are investigating.