An 'unspeakable tragedy': Connecticut town stunned by arrest of 12-year-old in killing of twin sister, stabbing of mother The boy is facing juvenile charges of murder and first-degree assault.

A 12-year-old boy allegedly killed his twin sister by stabbing her in the neck and torso and attacking his mother, a prominent lobbyist, in what a family friend described as an "unspeakable tragedy" in their Connecticut home, officials said.

Brigid Curtin was identified Wednesday as the 12-year-old who was killed by her brother in their West Hartford home, according to the Hartford County Medical Examiner's office. Brigid suffered stab wounds to her neck and torso, a medical examiner official told ABC News.

Brigid's brother also allegedly stabbed his mother, identified by her employer as Janemarie Murphy, 56, who survived the eruption of domestic violence Monday afternoon, police said.

The boy was taken into custody after his mother called 911 about 3:30 p.m. "saying she and her daughter had been stabbed by her son," according to a statement from the West Hartford Police Department.

"Officers arrived on scene and located the two victims and the suspect," the statement reads. "Officers, later joined by paramedics from the West Hartford Fire Department, immediately began emergency medical efforts to treat the mother and daughter."

Brigid and her mom were taken to St. Francis Hospital and Medical Center in Hartford, where the young girl died, police said. Murphy was listed in stable condition, police said.

The attack remains under investigation and police declined to comment on a possible motive. Investigators continued on Wednesday to search the family's two-story home, which has a holiday wreath hanging on the front door and decorative reindeer on the front lawn.

John Droney, an attorney for Murphy and her husband, Timothy Curtin, declined to comment when contacted by ABC News.

The boy, whose name has not been released, was also injured in the attack, police said. He was arraigned Tuesday in his hospital bed at Connecticut Children's Medical Center on one count of murder with special circumstances and first-degree assault, officials said. The boy has been remanded to the custody of the Connecticut Judicial Marshals, police said.

Officials said he is too young to be charged as an adult.

"This is truly an unspeakable tragedy," Chuck Coursey, a friend of the Murphy-Curtin family who is serving as their spokesman, said at a news conference on Tuesday.

"I think that the first thing we all understand is there are no answers and things are difficult to explain," Coursey said.

Janemarie Murphy worked as a lobbyist for the Hartford law firm Murtha Cullina LLP.

"We are devastated by the horrific tragedy affecting our friends and colleague Jane Murphy," the law firm said in a statement. "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 asked everyone to please respect their privacy during this extraordinarily difficult time."

Prior to joining Murtha Cullina, Murphy served as a legislative aide to the Connecticut State Senate Majority office and the Senate president pro tem, according to her bio on the law firm's website.

Officials said her two children were seventh graders at Sedgewick Middle School in West Hartford, where records showed they were both honor students last year.

"As mayor, this is just the worst nightmare to have a tragedy like this," West Hartford Mayor Shari Cantor said at Tuesday's news conference. "To lose anybody in your community is very difficult, but when it affects a family so deeply it's just tragic."

On Tuesday night, a prayer vigil was held for the family at Westminster Presbyterian Church in West Hartford.

"Like many in the West Hartford community, we are deeply anguished over the recent tragedy that took place in our town," Rev. Julie Emery, the pastor of the church, said in a statement. "Our prayers are with the family affected, with the young people and parents in our community who are struggling to make sense of it all, and the emergency response workers, teachers and counselors who are working to find words of comfort and offer safe space for all of us."