A teen brother and sister were shot to death by their mother's boyfriend, who then turned the gun on himself following an argument at their Watertown, Connecticut, home, authorities said.

Police responded to the home just before 10 p.m. on Tuesday after a woman called 911 to report that her boyfriend had shot her children.

When officers arrived, 15-year-old Della Jette and 16-year-old Sterling Jette Jr. were found with life-threatening injuries, the Watertown Police Department said in a news release. They died at the hospital.

The boyfriend, identified as Paul W. Ferguson, 42, was pronounced dead at the home from a self-inflicted gunshot wound, according to police. The mother was at home when the shootings occurred and was not injured.

Watertown police said there was an argument before the shootings between Ferguson and one of the teenagers. Police chief John Gavallas said at a press conference Wednesday that Della was upset over Ferguson's smoking cigarettes in the home and raised the issue with her mother.

"It became a little bit loud," Gavallas said. "Ferguson was downstairs with the son watching TV. He came up and told the daughter to quiet down and not talk to her mother that way. They had a bit of a dust-up back and forth."

Gavallas said Ferguson went into a bedroom, got a gun and shot Sterling in the leg when the teen came upstairs to confront him. Della went out onto a deck and the mother ran downstairs to call for help.

Ferguson followed Della out onto the deck and shot her in the chest before coming back inside and shooting Sterling in the chest, the chief said.

Ferguson then locked himself in a bedroom and shot himself, police said.

"The deaths of these children is a tragedy for our whole community and the police department extends our deepest sympathy to the victims' mother, family and friends," the police department said in its news release.

Della and Sterling were both students at W.F. Kaynor Technical High School in Waterbury.

"There is nothing worse that can happen to a school community. Our number one priority right now is doing all we can to support our students, staff and families through this crisis," said the state's superintendent of technical education, Jeffrey Wihbey, in a statement.

The brother and sister had previously attended Watertown Public Schools through the eighth grade, superintendent Rydell Harrison said.

"The Watertown community has suffered a tremendous loss," the superintendent said in a statement on Twitter. "Our school community, like the wonderful town we live in, will come together to do everything we can to provide support to our students, staff and families during this difficult time."

Ferguson, a convicted felon who was not legally allowed to be in possession of a gun, moved into the home about two weeks ago, police said.