(CNN) -- Aaron Alexis -- the man authorities say is responsible for killing 12 people at the Washington Navy Yard -- told Newport, Rhode Island, police last month that an individual "had sent three people to follow him and to talk, keep him awake and send vibrations into his body," according to a police report. According to that report, which is related to an investigation into a harassment complaint at a Marriott hotel in Newport, Alexis said he first heard the people "talking to him through a wall" at a Residence Inn in Middletown, Rhode Island, where he'd been staying. He packed up and went to an unidentified hotel on a Navy base in Newport where he heard the same voices talking to him. He moved to a third hotel, the Marriott, according to the police report. There, Alexis first told authorities that the three individuals spoke to him through the floor and then the ceiling. Alexis said the individuals were using "some sort of microwave machine" that sent "vibrations through the ceiling, penetrating his body so he cannot fall asleep." He told authorities, according to the police report, that "he does not have a history of mental illness in his family and that he never had any sort of mental episode."