BOSTON -- No charges will be filed in connection with a motor vehicle crash in Marblehead that claimed the life of a teenager.

Alessandra Castner was struck shortly before 7 p.m. on Aug. 24 near 262 Pleasant St. by 19-year-old Thomas Larivee, of Salem.

"After a thorough investigation that included dozens of interviews, a forensic analysis of the driver's Blackberry and a state police collision reconstruction, the conclusion is that the accident was unavoidable," Worcester District Joseph D. Early Jr. said. "With no evidence to establish the commission of a crime, no charges will be brought."

Castner suffered a serious head injury when she was hit while crossing the street and was transported to Salem Hospital by and later taken by medical helicopter to Boston Medical Center, where she died.

"Other than the victim and Mr. Larivee, no other eye witnesses to this accident were identified," Early said. "The first person on the scene was a driver who was traveling in the eastbound lane, which is the opposite direction that Mr. Larivee was traveling."

In Larivee's statement to police he said he never saw the victim prior to striking her. He said he was traveling about 25 to 30 mph when he heard a "thump" and then saw the victim going over his vehicle. A state police collision reconstruction calculated the Volvo's speed at 21 mph at the time of impact.

Police at the scene determined that Larivee was not under the influence of drugs or alcohol through field observations at the time of the accident. The observations were confirmed by a preliminary breath test that revealed no alcohol in his system.

Larivee’s Blackberry was forensically analyzed by the State Police Crime Lab. The analysis revealed that there were no incoming or outgoing calls or text messages at the time the accident occurred.

Investigators said the victim was about 8 feet into the crosswalk when she was struck.

"Trooper Bibeau, who has conducted more than 500 collision reconstructions in 13 years, concluded that the driver did not have enough time to recognize a person in the crosswalk and react," Early said. "Based on the trooper’s analysis and the evidence available, this tragic accident was unavoidable."