Three girls visiting their father found dead days after going missing

Three young sisters who were visiting their father were found dead after going missing for days. Their likely cause of death has been revealed.

Fox 13 Seattle reported that Olivia, 5, Evelyn, 8, and Paitlyn, 9, had a planned visitation to their dad Travis Decker last May 30. They didn't return home that day.

Their bodies were discovered on June 2, at the Rock Island Campground in Chelan County in Washington State.

A preliminary report filed with the Chelan County Superior Court stated that their likely cause of death was asphyxiation.

Decker, a former military member with extensive training, is now missing and has been accused of killing his children. Authorities launched a manhunt for him.

His vehicle was near the Rock Island Campground and had "two bloody handprints" and "personal items such as blankets, food, car seats and a wallet on the center console," according to Fox 13 Seattle.

The camp also showed signs of recent activity, with a tent and cooler located a short distance away.

According to court documents, Decker's cell phone activity showed that he drove to and left the same campground a day before the alleged kidnapping.

When authorities called him during the scheduled return of the girls, it went straight to voicemail. He couldn't be contacted since.

PEOPLE Magazine, citing the Wenatchee Police Department, said Decker has been charged with three counts of first-degree murder and one count of kidnapping. He's also facing custodial interference charges.

"It is unknown whether Decker is currently armed, but he may pose a significant risk, if approached," the police said.

Last June 1, the Wenatchee Police Department, in a statement, said the three girls were last seen at around 5 p.m. on May 30. It noted that Decker is "homeless and living in his vehicle or at various hotels/motels or at campgrounds in the area."

"The visitation was part of a parenting plan, but he has since gone outside the parameters of it which is not normal and cause for the alarm," it said.

Fox 13 Seattle, citing interviews with Decker's ex-wife, reported that there's a possible decline in his mental health leading up to the alleged kidnapping and murders.

According to court documents, his ex-wife claimed he was diagnosed with borderline personality disorder and that he doesn't take medications for it.

He and his ex-wife had been divorced for several years and had a parenting plan. According to the plan, Decker was allowed to see their children during specific hours every other weekend in the Wenatchee Valley. He must also seek mental health treatments and anger management counseling. But he wasn't allegedly following the plan, and he allegedly didn't sign it.

Decker was reportedly "quieter than usual" when picking up the kids for visitation, which was "out of character" for him. He had also allegedly been talking about getting rid of his dog amid housing and money issues.