Law enforcement has tracked someone they believe to be Travis Decker – accused of killing his own children – in the Blewett Pass area of Washington state Tuesday evening, the Chelan County Sheriff’s Office said in a news release.

The Chelan County Sheriff’s Office received a tip of a hiker who appeared to be “ill prepared” for the trail and weather conditions, and was avoiding other people, a news release said.

“Tracking teams immediately acted upon the information and spotted a lone, off trail hiker from a helicopter near Colchuck Lake who ran from sight as the helicopter passed,” it said. “Additional assets were called to the area while they developed a plan to track the individual. Teams later picked up a trail and deployed K9s to the area, tracking the subject to the area of Ingalls Creek Trailhead on HWY 97.”

Law enforcement is asking that anyone who lives in the area to lock their homes and cars and report suspicious activity.

“Tracking teams believe they are on Decker’s trail, community support and tips are still needed!” the sheriff’s office said.

Decker, 32, hasn’t been seen since May 30. His three daughters – all under age 10 – were found on June 2, suffocated at an isolated, abandoned campsite east of Seattle.

Since then, an intense manhunt over hundreds of square miles has unfolded, the sheriff’s office said.

The United States Border Patrol has taken command of the operations and search for Decker, which also utilized National Guard members, the release said. Detectives at the sheriff’s office “remain strongly engaged on the murder investigation.”

The father is charged with the aggravated murder and kidnapping of the Decker sisters: Olivia, 5, Evelyn, 8, and Paityn, 9. With federal agents now involved in the search for him, Decker also faces a federal charge of Unlawful Flight to Avoid Prosecution. A reward of up to $20,000 is offered for information leading to his arrest.

Decker’s truck, his dog and “many of the suspect’s personal items” were found about 75 yards from the girls’ bodies, the sheriff’s office has said. Some blood on the truck belonged to a human male, while other blood was not human, it said, citing testing. The dog was given to a local humane society, the sheriff’s office said; the welfare agency won’t “release information about any animals in custody involved in an active case.”

Gov. Bob Ferguson has authorized emergency funding so National Guard helicopters can help in the search for Decker.

The rugged terrain of the Cascades – along with Decker’s own survivalist history – are proving challenging for law enforcement agents trying to catch up to him.

Suspect had survival training and an interest in Canada, court documents say

Decker, a veteran of the war in Afghanistan, “frequently engaged in hiking, camping, survival skill practice, hunting and even lived off the grid in the backwoods for approximately 2.5 months on one occasion,” US Marshal Keegan Stanley said in an affidavit.

Four days before his disappearance, Decker made several Google searches related to finding a job in Canada, as well as “how does a person move to canada,” Stanley said.

Decker’s truck and the children’s remains were found less than a dozen miles from the Pacific Crest Trail, a 2,650-mile path that runs all the way to the Canadian border. From the area closest to Decker’s campsite, it is about a 200-mile hike to Canada.

Searchers with the Chelan County Sheriff’s Office spent several days looking for Decker in the area around his campsite, with recreation areas around the Icicle River temporarily closed.

Late Monday night, the sheriff’s office said it had narrowed the search to the Ingalls Creek area west of Wenatchee, the county’s largest city and about 15 miles southeast of the campsite across rough terrain.

“During any criminal investigation, including this one, there is law enforcement sensitive information that is not shared with the public in order to protect the integrity of the investigation,” the sheriff’s office said. “We appreciate the public’s patience, understanding and cooperation during this complex and emotional investigation.”

Decker had mental health issues, ex-wife says

Decker has not been seen since he picked up the children May 30 from their mother for a scheduled, three-hour visit, his ex-wife said, according to a state court affidavit. Although the exchange “occurred without issues,” Whitney Decker later said he “was quieter than usual.”

She advised investigators Travis Decker had been diagnosed a few years ago with borderline personality disorder, which the Cleveland Clinic describes as involving “extreme mood fluctuations, instability in interpersonal relationships and impulsivity.”

Travis Decker had served in the US Army for eight years, an Army spokesperson said. He is in the Washington National Guard, facing discipline for missing required drills, a Guard spokesperson said. CNN has reached out to the Department of Veterans Affairs about whether Decker has sought treatment for mental illness through its facilities.

Decker had refused to sign his and Whitney’s most recent parenting agreement, which required him to seek mental health treatment and anger management, she told Wenatchee Police. He was homeless at the time of his disappearance, she said, living in motels and campgrounds.

‘Living every mother’s worst nightmare’

Whitney Decker called police after her ex-husband failed to show up with their daughters as planned at 8 p.m. on May 30. The custody agreement does not allow Travis Decker to keep the children overnight.

The children were discovered three days later with plastic bags over their heads, their wrists tied. The cause of death was suffocation, the medical examiner said.

“Whitney is living every mother’s worst nightmare,” family friend Amy Edwards said in a statement released by Whitney Decker’s attorney. “The hole in her heart is immeasurable. There are no words that can capture the weight of this loss.”

CNN’s Alaa Elassar, Natasha Chen and Amanda Jackson contributed to this report.

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