A 12-year-old Connecticut boy was charged with murder after he fatally stabbed his twin sister and injured his mother who is a prominent lobbyist, according to reports.

The boy, who has not been named, was charged Tuesday with one count of murder and one count of first-degree assault, West Hartford police said. The boy was arraigned at Connecticut Children’s Medical Center, where he was treated for minor injuries following the stabbing that seriously injured his mother, Janemarie Murphy, 56, and killed his 12-year-old sister, Brigid Curtin, the Hartford Courant reported.

Police received a 911 call about 3:30 p.m. Monday from a woman who said her son stabbed her and her daughter. Officers arrived at the scene to find all three at the home.

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They were rushed to the hospital where the girl later died. The state medical examiner on Wednesday ruled her death as a homicide due to the stab wounds to her neck and torso, FOX61 reported.

Murphy, a well-known lobbyist at the state Capitol, was identified by her employer, Murtha Cullina LLP, as the victim in the stabbing. Murphy is said to be in hospital in stable condition.

“We are devastated by the horrific tragedy affecting our friend and colleague Jane Murphy,” the Connecticut law firm said in a statement to the Hartford Courant. “Jane has been a valued member of the Government Affairs Group of Murtha Cullina LLP for over 24 years. We are doing all we can to support Jane and her family, and ask everyone to please respect their privacy during this extraordinarily difficult time.”

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Connecticut Sen. Chris Murphy tweeted his condolences Murphy and her family.

“My heart is sick for my friend Janemarie Murphy and her family,” Murphy tweeted. “What an unfathomable loss. I know the community of West Hartford and her legions of friends at the State Capitol are rallying to her side to make sure the family has all they need.”

The motive of the fatal attack remains under investigation. Murphy’s children attended Sedgwick Middle School.

“There are a thousand parents out there looking for answers,” State Sen. Beth Bye told the Hartford Courant. “It’s going to be a community healing process.”

West Hartford Mayor Shari Cantor released a statement from the family, which has asked for privacy.

"We are all enduring a very painful and unimaginable loss," the statement says. "Our family will never be the same. Our daughter was a beautiful child and we will remember forever her smile ... laughter . and remember her for the way she loved and lived."

The Associated Press contributed to this report.