JUNEAU, Alaska (AP) — Authorities investigating the deaths of three children who were shot by their 15-year-old brother have not found any evidence that the shootings were planned, an Alaska State Troopers spokesperson said Thursday.

There also were “no obvious reasons for why he shot three siblings and took his own life,” troopers spokesperson Tim DeSpain said.

“The only person — people — that know what really happened in that moment are deceased,” he said. Investigators were confident that this was not an accident and confident that it was not planned, he said.

Troopers on Wednesday said an investigation revealed that a 15-year-old boy the prior afternoon shot three siblings and then fatally shot himself in a home near Fairbanks. The parents were not home at the time of the shootings, the statement from troopers said.

Three other siblings in the home, who are under the age of 7, were not hurt, troopers said. They “were not in the same part of the house” when the shots were fired, DeSpain said.

The children who died were 5, 8, 15 and 17 years old, DeSpain said.

DeSpain said after the shots were fired, a neighbor went to the home, discovered the bodies and called 911.

Troopers have not released any names, and it wasn’t clear when they might. There are “aspects to the investigation that don’t warrant” releasing the names of those who died at this time, he said.

DeSpain has said the gun was a “family gun but beyond that, it’s all still part of the ongoing investigation.”

Fairbanks is about 360 miles (580 kilometers) north of Anchorage.

Alaska Gov. Mike Dunleavy on social media Thursday said he and his wife “want to extend our sorrow and prayers to the family of this terrible tragedy. Please join us in lifting them up in prayer.”

Shannon Watts, founder of the group Moms Demand Action, which advocates for public safety measures to help guard against gun violence, tweeted a link to an article about the shooting on Wednesday. In a statement Thursday, she said: “An entire family and community are forever traumatized by a horrific, preventable act of gun violence because a 15-year-old was able to access a gun.”

The shooting comes after a woman earlier this month was charged in the deaths of two men in Anchorage. The Anchorage Daily News reported a prosecutor in the case said the killings lacked a clear motive but said the woman also had told detectives she had wanted to become a serial killer since she was a child.

In 2015, authorities determined that a man had killed his girlfriend, her two children and then himself the year before in Kenai. The family had disappeared in 2014, and their bodies were found the following year near the family home.