A police officer was arrested after an alleged DUI crash killed a 21-year-old New Hampshire woman, according to New Hampshire State Police.

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Police say officers in Amherst responded about 11:30 p.m. Friday to a serious crash on Route 101, and responding officers found two vehicles at the scene.

After an initial investigation, police say a pickup truck, driven by off-duty Londonderry police Officer Tyler Berry, 27, of Amherst, was traveling westbound when it crossed the yellow center line and struck a Hyundai Santa Fe head-on as it was heading eastbound.

The driver of the Hyundai Santa Fe was identified as 21-year-old Manchester native Sierra Croteau, who was pronounced dead at the scene.

"It's just a devastating thing," said Kristin Matteau, the mother of the victim's boyfriend. "You have no idea what just rushes through your head."

Croteau lived with Matteau and her family. She said the 21-year-old was headed back to their home in Manchester, Massachusetts, after visiting her mother in Milford.

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"She had just got out of work, I think at 9 or 10 o'clock at night. She went to her mother’s to visit a little bit," Matteau said. "And she left there to come home, and Tyler left her two messages on her phone and she never replied. Quarter of 4 this morning we found out why."

Berry was seriously injured in the crash and taken to Catholic Medical Center in Manchester, and was eventually arrested at the hospital and charged with felony aggravated driving under the influence of alcohol.

Kim Bernard, operations captain for the Londonderry Police Department, confirmed that Berry worked for the department.

Londonderry police released a statement Saturday regarding Berry's arrest and his involvement in the crash:

“The Town of Londonderry and the Londonderry Police Department have been informed of the tragic events which unfolded last night in Amherst, New Hampshire involving Sierra Croteau and Londonderry Patrol Officer Tyler Berry. First and foremost, we send our heartfelt thoughts and prayers to the family and friends of Sierra Croteau. 

“It is our understanding that Tyler Berry has been arrested and charged in connection with this matter. As his employer, we will cooperate fully with the investigation and take appropriate action when more facts are known.”

Croteau was a licensed nurse assistant for BrightStar Care. The organization issued a statement after learning of the woman's death:

“We are shocked and saddened to learn of Sierra's tragic passing. She will be greatly missed by the whole BrightStar Care family. She was a wonderful girl with a caring heart and a positive attitude. Our deepest condolences to her family, friends, clients, and co-workers.”

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"She was a very sweet girl. She would do anything for anybody. She was always there when I need her. I'm going to miss her spirit, her goofiness. She was very fun person to be around," Matteau said of the victim. "Everyone is going to miss her."

Route 101 in the area of Manchester Road was closed for about five hours due to the crash, and the investigation into the incident is ongoing.

– The Associated Press contributed to this report.