Fourth Arrest Made in ‘Gruesome' Murder of Marshfield, Mass. Man

Mark O’Brien of South Boston was arrested overnight Tuesday and will be arraigned Wednesday

A fourth arrest has been made in the gruesome death of a Marshfield, Massachusetts man.

Mark O’Brien of South Boston was arrested overnight Tuesday and will be arraigned Wednesday. He is facing murder and burglary charges related to the death of Robert McKenna.

McKenna was found dead in his Damon Point Road home on Sept. 17. Prosecutors described the scene as "horrific," saying that he died of excessive blood loss from stab wounds to his upper arm, hands and head. On Sept. 28, James Ferguson was arrested on murder and burglary charges.

Michael Moscaritolo,32, and his girlfriend, 31-year-old Lauren Kalil, both residents of Quincy, were arrested in October.

Moscaritolo and Ferguson allegedly stole assault weapons from McKenna's home. Police recovered five guns that were stolen from the home. McKenna owned four of them, including an AR-15 and an AK-47.

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