What happened the night of the Dennis boat crash that killed Sadie Mauro? What we learned.

BARNSTABLE − A 19-year-old Medfield man pleaded not guilty to all charges regarding a Dennis boat crash that left a 17-year-old girl dead in July.

David K. Sullivan allegedly drove the boat that crashed in Sesuit Harbor on July 21, killing Sadie Mauro, a lacrosse player and rising senior at Dover-Sherborn High School in Dover.

Sullivan was arraigned in Barnstable Superior Court on Tuesday morning on charges of death of a person caused by operating vessel/boat under the influence of intoxicating liquor; possession of false RMV documents; minor in possession of alcohol; two counts of operation of a vessel while under the influence causing serious bodily injury; and reckless or negligent operation of a vessel causing death.

David Meier, a partner with the Boston law firm Todd & Weld, declined comment as he and Sullivan exited the courthouse. But in a previous statement to the Times, he called the crash an accident.

"What occurred that night was an unimaginable tragedy. But what occurred was an accident -- in every sense of the word. These criminal charges only compound that tragedy for everyone involved," said Meier.

Assistant District Attorney Colleen Duarte also declined comment.

Sullivan was ordered released on $5,000 bail with the condition that he surrender his passport. His next court date is Dec. 14.

A police report was not available at Barnstable Superior Court.

In the July 21 crash, a boat struck a jetty around 9 p.m. Two other people on the boat were also injured, according to the district attorney's office.

The boat bore an Alabama registration and had six people on board at the time of the crash, according to a state police statement at the time. The staff at the Northside Marina, a marina at Sesuit Harbor, confirmed on July 24 that the boat, a Regulator 26, had been docked there.

Mauro’s body was recovered from the harbor around 11:30 p.m. by Dennis fire and regional dive team personnel, state police said at the time.

What happened the night of the Dennis boat crash?

Mauro was "Mr. Sullivan's girlfriend — and best friend," according to a memo on bail conditions filed by Meier. According to Sullivan's account outlined in the memo, Sullivan was thrown from the boat after the crash.

"In the darkness, he managed to swim back to the still-running boat, maneuver his way on board, and shut off the engines," reads the memo. "Within seconds, he dove back into the water in search of his girlfriend and the other individuals who had been on the boat."

Sullivan found a male, who he pulled through the water and lifted onto the boat, according to the memo. He then called the Coast Guard "9-1-1" channel, identified the boat's location, and described its condition. As the Dennis Fire Rescue boat and other emergency personnel arrived, Sullivan repeatedly yelled "into the darkness of the harbor the names of his girlfriend and the other young men who had been on the boat."

The memo says Sullivan remained on the dock area for about an hour after the incident to interact with various rescue personnel and responding police officers. He gave police and rescue personnel the names of each person on the boat.

Within an hour of the incident, Sullivan interacted a second time with police investigators who came to his family home in Dennis to meet with him. After midnight, Sullivan saw police investigators a third time at the Dennis police station.

The memo asserts that Sullivan was never asked to perform field sobriety tests, submit to a portable breathalyzer test or take a blood test "whether on the harbor dock, outside of his family home, or at the Dennis Police Station."

The judge also allowed a motion by Meier to preserve evidence regarding the crash, including all notes, body-worn camera audio and video recordings, and typed or written communications made by any law enforcement member involved in the investigation or prosecution.

Sullivan graduated from high school in June, according to court documents. Six weeks ago, he moved into his college dormitory to begin his freshman year in college.

Criminal investigation

In August, Galibois announced authorities had launched a criminal investigation into the crash, in which a boat struck a jetty around 9 p.m. leading to the death of Mauro and injuring a teenage boy. His office was joined in the investigation by Dennis police, state police, Massachusetts Environmental Police and regional and state police dive teams.

Mauro, of Sherborn, was committed to Gettysburg College in Gettysburg, Pennsylvania, to play college lacrosse. When Principal John Smith announced her death in an email to the school community, he remembered her as having "a heart of gold and the sweetest spirit."

"She had such a strong sense of self and had a love for adventure and anything outdoors. A hardworking student and great athlete, Sadie was genuine and effortlessly kind," said Smith.

Sullivan was indicted by a Barnstable County grand jury for his alleged role in the crash in late September, according to a written statement released by Galibois earlier this month.

Zane Razzaq writes about housing and real estate. Reach her at zrazzaq@capecodonline.com. Follow her on Twitter @zanerazz.

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This article originally appeared on Cape Cod Times: Dennis boat crash: Court memo tells story of night Sadie Mauro died