The search for Travis Decker, a former U.S. Army soldier accused of killing his three young daughters in Washington state, is in its second week as the Washington National Guard has been deployed to aid law enforcement officers continuing to comb the Cascade Mountains and the Pacific Crest Trail region.

Exactly what prompted the search to narrow was not made public. The Wenatchee man is accused of killing his three daughters, then vanishing.

Investigators have been looking for Travis Decker since May 30. Three days later, a sheriff's deputy discovered the bodies of his three young daughters.

Travis Decker, accused of killing his three daughters in central Washington, remains at large after being spotted in Idaho, while federal agents have joined the search for him.

Authorities are searching for the girls' father after their bodies were found zip-tied and with plastic bags over their heads in a remote part of Washington state.

Travis Decker, the father accused of murdering his three young daughters, lacked mental health resources and struggled with PTSD, his ex-wife's attorney told ABC News.