Manhunt Underway For Father After 3 Young Daughters Found Dead in Washington State

Three young sisters who went missing while visiting their father were found murdered in Washington state -- and now we know how they were apparently killed, 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 a campground 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 already been charged with his daughters' deaths ... 3 counts of first-degree murder, and one count of kidnapping, according to police.

Fox 13 Seattle reports Decker's pickup truck was smeared with 2 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, and a tent and cooler were also discovered nearby.