An 18-year-old former student at Devereux Glenholme School in Washington will be prosecuted as an adult on strangulation and assault charges.

Robert Messina-Toombs, 17 at the time of his arrest in February 2012, is charged with first-degree robbery, first-degree assault and first-degree strangulation for an alleged attack on a Glenholme staff member.

The attack on Edward Zeiner, then a cottage staff member at the school's Holly House, allegedly took place June 21, 2011, court documents state.

Judge James P. Ginocchio of Superior Court in Litchfield ruled Jan. 15 that Mr. Messina-Toombs will be charged as an adult.

Mr. Messina-Toombs, a New York City resident, has pleaded not guilty. He is free on $500,000 bond, with his next court date scheduled Feb. 26.

He had been enrolled at Glenholme for approximately two weeks before the alleged attack, court records show.

His attorney, Hubert Santos, declined to comment on the charges.

Glenholme School is a specialized boarding school that provides therapy for children with behavioral and learning problems.

The staff is trained in behavioral health care, according to the school's website.

Patrick Queenan, clinical director at the school, said in a prepared statement "this behavior is not typical for our students."

"We have taken this incident very seriously and been in full partnership with local police throughout the investigation," Mr. Queenan's statement continues. "Our focus is always on providing ... a safe and rewarding work environment for our staff."

In October 2012, Mr. Zeiner filed a personal injury suit against Mr. Messina-Toombs in U.S. District Court.

The suit was brought for "assault and battery, attempted murder, and intentional inflection (sic) of emotional distress."

The suit claims Mr. Zeiner suffered "neck and back injuries," has "because of the blows to his head... suffered headaches and severe hearing loss," and has been diagnosed by mental health providers as "having post-traumatic stress disorder as a result of the attack."

The suit states Mr. Zeiner "blacked out" when Mr. Messina-Toombs put him in a "choke hold" as he searched Mr. Zeiner's person for vehicle keys. When Mr. Zeiner came to, he allegedly was "punched to the head" and "dragged down the back steps."

At the bottom of the steps, Mr. Zeiner was allegedly "picked up and slammed to the ground," followed by Mr. Messina-Toombs tying first a shoe lace and then a belt around Mr. Zeiner's neck.

Mr. Zeiner's yells for help allegedly caused his attacker to flee. Mr. Messina-Tombs was later located by police and placed under arrest.

A motion for default judgment in the personal injury case was filed Dec. 12, 2012 for Mr. Messina-Toombs' failure to appear or to plead in the action.

Mr. Santos, who is also representing Mr. Messina-Tombs in the personal injury suit, declined comment. The suit is now before Magistrate Judge Holly B. Fitzsimmons.