BARRINGTON — Patrick Murphy, who died riding the waves of the Barrington River while being towed by a high-speed boat, didn’t drown Tuesday night.

Instead, he was killed by blunt force trauma and being slashed by something sharp, probably a propeller.

In the wake of Murphy’s autopsy, the state upgraded the charge against the driver of the boat, Ryan A. Greenberg, 17, of 33 Lamson Rd., to one felony count of reckless operation, death resulting. He also faces a misdemeanor count of refusing to submit to a chemical test.

The owner of the 21-foot Seminole speedboat said yesterday evening that he does not know how Murphy, Greenberg, and one other person whom the police have not identified, obtained the boat.

The Office of the State Medical Examiners reported yesterday that Murphy, a 17-year-old Barrington High School student, died from “blunt and sharp force injuries.”

“Law enforcement officials are going on the assumption that the boat’s propellers caused the cuts,” said Michael J. Healey, spokesman for Attorney General Patrick C. Lynch.

Whether Murphy, who was not wearing a life vest, was impaired is not known. Toxicology tests, which are routinely done in such cases, could take up to three months, according to Health Department spokeswoman Andrea Bagnall Degos.

But the police have said that alcohol was involved in the death.

Liquor was found on the boat and Greenberg failed a field sobriety test.

Immediately after the accident, Greenberg was charged in District Court, Providence, with one count of reckless operation of a motorboat and one count of refusing a chemical test, both misdemeanors. The Department of Environmental Management said the boat was being operated at Hundred Acre Cove.

Greenberg was released on $5,000 personal recognizance.

“The misdemeanor charges were filed when law enforcement was operating under the assumption that the victim might still be alive, which the police were led to believe,” said Healey.

But Wednesday afternoon, Murphy’s body, clad in a yellow swimsuit, was recovered below the surface of the river about 100 yards north of the East Bay Bike Path bridge. That’s more than a mile downriver from where DEM said Greenberg was operating.

Yesterday, the reckless operation charge was upgraded to the felony charge.

Healey said that after Greenberg is arraigned Friday, the case would be taken to a grand jury.

The maximum penalty is 10 years in prison.

Barrington police are also considering filing their own charges in the case. Interviews are continuing and the police are still looking for witnesses who might have seen what happened on the water Tuesday night.

It is not known whether the third person who was with the boat that night will face charges.

The owner of the boat, Andrew Davis, of 6 Spindrift Way, said last night that neither he nor any member of his family was on board.

Davis said his boat is kept at the Barrington Yacht Club and he does not know how the boys obtained it.

Davis’ 16-year-old son, Turner, was a lacrosse teammate of Murphy’s.

“I wish I knew more,” Davis said. “Really, we just feel terrible for the family. It’s horrendous. We feel horrible our boat was involved.”

Davis said he has been interviewed by the police.

The boat has been impounded by the Department of Environmental Management.

Yesterday, the DEM refused to provide basic registration information on the vessel, effectively withdrawing a record that is routinely public.

Spokeswoman Gail Mastrati said the record identifying the registered owner of RI-1552U “is part of an active investigation, and therefore records are exempt from public disclosure at this time.”

The Journal obtained the records from another source.

They show that the 21-foot-long Seminole is Davis’ newest boat. He also owns three other powerboats: a 30-foot 1996 Bertram, a 27-foot 2004 Regulator and a 16-foot 2000 Boston Whaler.

With reports from staff writer W. Zachary Malinowski.

mwims@projo.com