Three young sisters who went missing while visiting their dad were found murdered in Washington state — and now we know how they apparently died as police search for their dad.

Paityn Decker, 9, Evelyn Decker, 8, and Olivia Decker, 5, likely died by asphyxiation, according to court documents, obtained by Fox 13 Seattle.

Police say the bodies of the sisters were discovered Monday after detectives traced the whereabouts of their father’s GMC Sierra pickup truck to an area near some campgrounds in Chelan County, WA.

Cops say the girl’s father, Travis Decker, has vanished and investigators have now launched a massive manhunt to find him.

What’s more, Decker has been charged with serious crimes in connection with the deaths, namely three counts of first-degree murder and one count of kidnapping, according to police.

Per Fox 13 Seattle … Decker’s pickup truck was smeared with two bloody handprints close to where the 3 corpses were found.

The outlet reported blankets, food and car seats were located inside the vehicle along with a wallet “on the center console.” A tent and cooler were also reportedly discovered nearby.