DOVER, N.H. – A man charged with killing a University of New Hampshire student in October initially told investigators that someone else strangled her and then said he accidentally killed her during a consensual sex act, according to documents unsealed Monday.

Seth Mazzaglia is charged with killing 19-year-old Elizabeth “Lizzi” Marriott, of Westborough, Mass., during an attempted sexual assault on Oct. 9. Prosecutors say it was not consensual.

Mazzaglia, 30, described several scenarios when questioned about the death, including that he had gone home and found her dead, with his girlfriend and another couple in his apartment, according to a police affidavit.

Mazzaglia later said he used a rope to strangle Marriott while they had sex, the police affidavit said.

The police affidavit also includes Mazzaglia’s account of dumping Marriott’s body in the Piscataqua River, Foster’s Daily Democrat reported. Marriott’s body has not been recovered.

Indictments allege an extensive cover-up by Mazzaglia, of Dover, and his then-girlfriend, Kathryn McDonough of Portsmouth.

Mazzaglia also faces a murder charge alleging he showed “extreme indifference to human life.”

A public defender representing Mazzaglia has declined to comment on the indictments.

Last week, Mazzaglia waived his arraignment on murder charges. He had been scheduled to appear in court Thursday after being indicted by a Strafford County grand jury.

McDonough, who was accused of lying to police about her whereabouts and interaction with Marriott, was indicted last month on charges of hindering the prosecution, conspiracy and witness tampering.

McDonough’s attorney, Ryan Russman, who sat alongside her in court in December, said then she was “obviously concerned.” Her parents had declined to comment.


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