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Medfield man, 19, indicted in Dennis boat crash that killed 17-year-old Sherborn girl

Sadie Mauro, the 17-year-old Sherborn girl who died in the boat crash.Mauro Family

A 19-year-old Medfield man is charged with operating a boat while under the influence during a July crash in Dennis that killed a 17-year-old Sherborn girl, authorities said Tuesday.

David Sullivan was indicted Friday by a Barnstable County grand jury on multiple charges in connection with the death of Sadie Mauro, including operating a boat under the influence of liquor, reckless or negligent operation of a vessel causing death, and two counts of operating under the influence of intoxicating liquor causing serious bodily injury, Cape and Islands District Attorney Robert J. Galibois’ office said Tuesday.

“The District Attorney would like to express his deepest condolences to the deceased 17-year old’s family and loved ones,” his office said in a statement, adding that it would make no further comment on the charges at this time. Sullivan is scheduled to be arraigned in Barnstable Superior Court on Oct. 10.

Sullivan’s lawyer, David Meier, said Tuesday that the crash was an accident.


“What occurred that night was an unimaginable tragedy,” said Meier, a partner at the downtown firm Todd & Weld LLP. “But what occurred was an accident in every sense of the word. These criminal charges only compound that tragedy for everyone involved.”

Around 9 p.m. on July 21, a Regulator boat registered in Alabama and equipped with twin 250-horsepower outboard engines crashed into a jetty in Sesuit Harbor with six people aboard, killing Mauro and seriously injuring two others, officials said.

After a fisherman on one of the jetties heard someone calling for help, authorities began launching boats to search for boaters who had fallen into the water, and the Coast Guard sent a helicopter from Air Station Cape Cod to assist.

An off-duty firefighter was first to reach the stricken boat and dropped anchor to keep it from drifting away, said Dennis harbormaster Dawson Farber. At the time, it wasn’t clear how many people had been aboard and who remained unaccounted for, he said.


Once rescuers realized that Mauro was missing, divers began searching for her and used sonar to find her body around 11:30 p.m.

Other passengers on the boat were treated at Cape Cod Hospital, including a teenage boy who sustained a head laceration, authorities said.

In early August, prosecutors said the probe into the crash had become a criminal investigation.

Mauro, who had previously lived in Shelburne, Vt., was a rising senior and lacrosse player at Dover-Sherborn Regional High School whom school officials described as a “great student, talented lacrosse player, and a great friend to many.”

“Sadie’s smile could light up a room; she had a heart of gold and the sweetest spirit,” Principal John Smith told families in a message in July. “She had such a strong sense of self and had a love for adventure and anything outdoors. A hard-working student and great athlete, Sadie was genuine and effortlessly kind.”

In an obituary, Mauro’s family said she loved “family and laughter, friends and sport, animals, and the outdoors.”

“She was born with a nature and wisdom beyond her years that allowed her to live a full life that felt far longer than her time here,” the obituary said. “Confident, warm, and empathetic in all she did, and to all she met, our lives will always be better and brighter because of her example.”


In an online profile, Mauro wrote about her experience as a lacrosse player as she prepared to start her junior year of high school. She hailed the leadership of her coach, who had brought the team to a state championship in 2022.

“I am determined and versatile on the field, and overall a very coachable player who is always eager to get better,” Mauro said. “Working as a team to achieve these successes, and being a starter this season has been extremely rewarding and motivating.”

John Hilliard of the Globe staff contributed to this report.

Jeremy C. Fox can be reached at Follow him @jeremycfox.