EAST LANSDOWNE, Pa. (AP) — Four of the five family members found dead in a house fire near Philadelphia were fatally shot by an adult male relative who also killed himself after setting fire to the home, authorities said Wednesday.

The youngest victim, a 10-year-old boy, was not shot but died of smoke inhalation, Delaware County District Attorney Jack Stollsteimer said as officials closed the investigation into the six Le family deaths in East Lansdowne.

Two police officers were shot and injured by Canh Le, 43, as they responded to the scene. Other officers dragged them to safety, and both are recovering.

Three generations of the Le family lived in the home, including grandparents who had come to the U.S. from Vietnam five decades ago and their two adult sons. Canh Le was single; his younger brother was married with three children.

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“They came here as refugees to build a new life, and they did so, in a beautiful community. In one full swoop, everything that they held dear is gone,” Stollsteimer said Wednesday as he announced the close of the criminal investigation.

The grandparents fled the home and called for help as the shooting began the afternoon of Feb. 7. They told authorities that their older son got a semiautomatic pistol from his bedroom after arguing with his 13-year-old niece.

He then used the long gun to shoot and kill the girl, her parents, her 17-year-old sister and himself, while also firing shots out the window at arriving police. Authorities said they will never know what prompted the argument.

“Nobody knows what, and nobody knows why. I’m never going to be able to answer that question for you,” Stollsteimer said at a news conference.

The victims include Xuong Le, 40; Xuong Le’s wife, Britni McLaughlin Le, 37; and the couple’s three children.

Authorities said they don’t know much about Canh Le’s life. Records suggest he had only one encounter with police during the many years the family spent in the area.

In 2006, he was charged with making terroristic threats, trespassing and disorderly conduct. Details of the incident remain unclear, but the first charge was later dropped and he completed a diversion program on the two lesser charges, leading him to serve 32 hours of community service and pay $1,400 in fines during a year of probation, according to court records.

One of the wounded officers, 44-year-old John Meehan of the East Lansdowne department, had surgery for a left forearm wound. Lansdowne Officer David Schiazza, 54, was treated for a leg wound.