MANSFIELD, Mass. (WPRI) — Police returned to the scene of a deadly shooting in Mansfield on Monday as the suspect was set to appear in court.

William O’Brien, 22, of Manchester-By-The-Sea, pleaded not guilty to charges of murder, carrying an illegal firearm, and carrying a loaded illegal firearm.

He’s accused of shooting and killing 23-year-old Samuel P. Waters on Saturday in the area of West Church Street.

There was a large police presence Monday morning near where the shooting took place. A Massachusetts State Police dive team was seen using cement pillars to slow the flow of the Rumford River and searching the water with metal detectors and magnets.

Police confirmed the search was part of the ongoing homicide investigation.

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Prosecutors allege O’Brien was seen wearing body armor in the street and ran off when police arrived. He was found a short time later and allegedly admitted to police what he had done, according to prosecutors.

The defense said there was more to what happened at the home, claiming there were weapons, drugs and cash inside.

O’Brien was held without bail following his arraignment. He’s due back in court June 22.

Prosecutors revealed in court that O’Brien was convicted in 2021 of carrying a firearm without a license and had a probation warrant out at the time of his more recent arrest.