Two young Duxbury, Massachusetts children are dead and a third is hospitalized as police investigate an incident at a home that they believe ended with the mother’s attempted suicide, authorities said.

A 5-year-old girl and a 3-year-old boy were pronounced dead at a local hospital after police were called to the Duxbury residence by a man arriving home, Bristol County District Attorney Timothy Cruz said at a Tuesday night news conference. An 8-month-old infant boy was hospitalized, he said.

The Duxbury Police Department received a call just after 6 p.m. from a man who returned to his Summer Street home to find what appeared to be an attempted suicide by the children’s mother, Cruz said.

Duxbury first responders brought the woman to a local hospital for treatment, where she remained as of 10 p.m. Tuesday, when Cruz addressed reporters in Duxbury.

In the home, police found three children all aged 5 and under, unconscious and with “obvious signs of trauma,” Cruz said.

“This is an unimaginable senseless tragedy,” he said. “This is not something that happened randomly.”

The 5-year-old girl and 3-year-old boy were rushed to a local hospital, where they were pronounced dead, Cruz said. The 8-month-old infant boy was brought by MedFlight to a Boston hospital, where he is being treated.

The five members of the home appear to all be related, and the woman appears to be the mother of the children, Cruz said. “But we’re still trying to put this together,” he added.

Duxbury Police Chief Michael A. Carbone said the situation appeared to be an isolated incident. “There is no further threat to the community,” he said.

Duxbury police are investigating the incident alongside the district attorney’s office and the Massachusetts State Police, Cruz said.

“As I’ve often said at these terrible events, this is a slow and steady process,” he said. “We’re not here to do it quick. We’re here to do it right.”