After 1 month search, dad accused of killing 3 kids could still be alive, expert says

It's been nearly a month since Travis Decker went on the run after allegedly killing his three young daughters near a Washington state campground, and at least one expert told ABC News he believes the fugitive father is likely still alive and will "eventually surface."

Paityn Decker, 9; Evenlyn Decker, 8; and Olivia Decker, 5, were killed after they left home for a "planned visitation" with Decker at approximately 5 p.m. on May 30, officials said. At approximately 3 p.m. on June 2, officials located the bodies of the three girls, and Decker's vehicle, near the Rock Island Campground in Chelan County, Washington.

Nearly one month later, the manhunt for Decker, an Army veteran, continues.

On Monday, officials said that "there is no certain evidence that Decker remains alive" or in the surrounding area after "seemingly strong early leads gave way to less convincing proofs over the last two weeks of searching."

"We can't and won't quit this search," Kittitas County Sheriff Clay Myers said in a statement. "Paityn, Evelyn and Olivia Decker deserve justice. Decker remains a danger to the public as long as he's at large."

But Todd McGhee, a law enforcement and security analyst and former Massachusetts state trooper, told ABC News he believes Decker is alive, especially since canines have "not picked up on any type of cadaver or any type of presence of a deceased body."

"Canines are trained to look for cadavers and sniff for those types of odors, so he's still maybe on the move," McGhee told ABC News.

McGhee said he believes Decker may have "slipped out of the U.S.," escalating the search into an "international manhunt." An affidavit previously revealed that Decker's Google searches leading up to the murders included "how does a person move to Canada" and "how to relocate to Canada."

Decker has likely been able to evade from law enforcement for so long due to his military training, which allows him to "navigate with limited resources in the wilderness," McGhee said. Chelan County Sheriff Mike Morrison previously said Decker's father revealed that his son had been known to go out and live "off the grid" for up to 2 and a 1/2 months.

Since he has managed to hide from officials for an extensive period of time, McGhee said Decker could have developed an escape plan, allowing him at least time to "process everything as far as turning himself in [and] standing trial."

McGhee said Decker will likely "leverage every bit" of his military experience but said he believes he will "eventually surface."

"He'll eventually have to surface through seeking shelter, seeking food, nutrition -- those types of things will require him to come out of hiding and, to some degree, expose himself to the general public," McGhee said.

Regardless of where Decker may be, McGhee said he is "confident" the search efforts will lead to some form of closure.

"I'm confident that something should reveal itself as far as a resolution as to where his existence is and hopefully a capture and an arrest," McGhee told ABC News.

What we know about the deaths of Paityn, Evelyn and Olivia Decker

On May 30, Decker picked up the girls, talked to his ex-wife, Whitney Decker, for about 15-20 minutes and then left, according to Arianna Cozart, Whitney Decker's attorney. While Whitney Decker had full custody of the children, Travis Decker was granted visitations to see the children for three hours on Fridays and eight hours every other weekend, so long as he remained in Wenatchee Valley with the girls, Cozart told ABC News.

"He said, 'Hey, I will see you at 8 [p.m.]' and he left, and he never came back," Cozart said.

Whitney Decker contacted police that evening with a civil complaint, saying she had not heard from Travis Decker and he had failed to bring the girls home at their scheduled time, officials said.

Detectives later learned Travis Decker and his daughters did not arrive at a "planned 5K running event" on Saturday. Officials believe that Decker traveled to the campground where the girls' bodies were found on May 29 and returned the next day with his three children, according to court documents.

When the girls were reported missing, the investigation had not met Amber Alert criteria, officials said, but an Endangered Missing Persons Alert had been issued through the Washington State Patrol.

When the bodies of the girls were discovered, there were plastic bags over the heads of each one and their wrists were zip-tied, according to court documents obtained by ABC News.

Around Decker's vehicle, deputies located zip ties and plastic bags "strewn throughout the area." The tailgate of the truck had what appeared to be "two hand prints of blood," according to court documents.

An autopsy determined the girls were suffocated, the Chelan County Sheriff's Office said on June 9.

Decker's mental health struggles, PTSD

Travis Decker had struggled with mental health issues, including PTSD, and was unable to access help through veterans' resources, Cozart said.

"The courts didn't fail these girls. It wasn't the judge and it wasn't Whitney; it was our system," Cozart said. "[Whitney] feels like the system really let Travis down. If somebody would have provided Travis with the help that he needed, those girls would be alive."

During a memorial service for the girls last weekend, Whitney Decker briefly spoke for the first time since her daughters' deaths. She said the girls had "warm and open hearts."

"I'm so thankful for the time that I had with the girls. I truly hope that the legacy of the girls' lives lives in everyone's hearts forever. They were incredible," Whitney Decker said at the memorial on June 20.

Decker, who is described as 5 feet, 8 inches tall with black hair and brown eyes, was last seen wearing a light shirt and dark shorts, police said, and a new suspect flyer was released by authorities on June 16. He is currently wanted for three counts of first-degree murder and three counts of kidnapping, police said.

Officials said anyone who has any information on Decker or knows of his whereabouts should call 911 immediately.