A federal arrest warrant has been issued for the Washington state man accused of killing his three daughters after taking them on a “planned visitation” last week.

The warrant charges Travis Decker with unlawful flight to avoid prosecution, KIRO reported. He has already been charged with three state counts of first degree murder and first degree kidnapping.

Decker took 9-year-old Paityn, 8-year-old Evelyn, and 5-year-old Olivia from their mother’s home late Friday afternoon and, according to the custody arrangement, was supposed to bring them back a few hours later because he was barred from keeping the girls overnight, as CrimeOnline reported. When he didn’t bring them back, Whitney Decker called police.

But the Washington State Patrol denied a request for an Amber Alert, saying it didn’t meet the criteria, and instead issued an endangered person alert, which does not go out to cell phones or get posted on highway message boards.

On Monday, investigators found Decker’s truck, and, nearby, the girl’s bodies with plastic bags over their heads and their hands ziptied. Decker was nowhere to be seen.

Corut documents say investigators believe he used his extensive military training and knowledge of wilderness survival to escape the area.

An affidavit filed with the federal warrant says that Decker conducted multiple searches on May 26 that included “how does a person move to canada,” “how to relocate to canada,” and “jobs canada.”

While divorce and custody documents filed over the past two years have revealed some indication that Decker’s mental state may have been deteriorating, a protection order petition filed by Whitney Decker this week provides even more information, KXLY reported.

In the June 3 filing, Whitney Decker wrote that her ex-husband “had seemed better, then it seemed like things just started happening one after another.” Among those “things” was workplace difficulties.

“His boss told him or told me that he had talked to Travis on Friday and he seemed like he was on the brink of something really extreme,” the petition says.

In previous months, the documents says, Decker had been receiving daily counseling from a Georgia pastor, but he abruptly ended those calls four weeks before taking the girls to kill them.  And a week before, he had a car accident that prompted a phone call to the girls telling them “he was going to jail.” He showed up on the mother’s doorstep later to apologize.

Then, she wrote, “Last week he tried to reconcile our marriage and had even made comments to the girls about him moving back in, and I rejected his advancements.”

Decker also reached out to a brother, who he hadn’t spoken to in years, and called his father, the document says.

Arianna Cozart, Whitney Decker’s attorney, said the fugitive father had been “engaged” with his children but that “the system let her children down.”

“It was the inadequacies in the services for our veterans that killed those children. That’s it,” Cozart said.