As the manhunt for the survivalist father accused of killing his three daughters before disappearing into the Washington wilderness sails past the one-month mark, local authorities are expressing their frustration as the trail begins to run dry."Im still angry," Chelan County Sheriffs Deputy Mike McLeod told USA Today as he recounted the search for 33-year-old Travis Decker. "He still hasnt been found."Decker, a former member of the U.S. Army and trained survivalist, is wanted for allegedly killing his three children Paityn; 9, Olivia, 5; and Evelyn, 8. The girls were reported missing by their mother, Whitney Decker, on May 30 after they did not return home from a court-mandated custody visit with their father.MANHUNT FOR FATHER ACCUSED OF KILLING 3 DAUGHTERS TAKES GRIM TURN IN WILDERNESSA single email received three days later led authorities to Deckers white GMC pickup at Rock Island Campground, where the girls family had told law enforcement he was likely headed for a camping trip, the outlet reported."At that point it was still a missing persons case," McLeod said. "Once I read the email, I knew right where they would be. But things went south fast."McLeod reportedly located the vehicle while searching the area on a dirt bike, subsequently alerting dispatch of his findings. The three girls bodies were found with their hands bound and plastic bags over their heads within mere feet of the truck.NEW FLYER SHOWS SUSPECTED KILLER DAD MAY HAVE CHANGED APPEARANCE IN WILDERNESS MANHUNT: POLICE"There was nothing we could do for them," McLeod said. "I was angry, where is he?"McLeod, a 20-year veteran with the sheriffs department who has spent the last nine years as a forest deputy, recalled finding Deckers wallet, noting it was the "only thing" left behind, the outlet reported.Roughly one mile from where the girls bodies were discovered, authorities reportedly found an abandoned orange tent.ALLEGED KILLER DAD COULD MAKE ONE MISTAKE THAT ENDS MANHUNT, SHERIFF SAYS"It looked like a homeless person tent," McLeod told USA Today. "Floor was ripped, haphazardly put up, not an expensive tent. However, the cooler was placed neatly next to it, squared up to the tent."Authorities reportedly believe the tent is tied to Decker, but an investigation has not yet determined who the owner is.Numerous local, state and federal agencies have continued to comb through the wilderness for the fugitive father while experiencing several environmental hurdles, according to Chelan County Sheriff Mike Morrison.SURVIVALISTS GOOGLE SEARCHES REVEAL POSSIBLE ESCAPE PLAN AMID MANHUNT IN DAUGHTERS TRIPLE MURDER: REPORT"We cant get into the river yet because of spring runoff," Morrison told USA Today, referring to the campgrounds Icicle River. Officials are unable to search the area until the water recedes which likely will not happen until July, according to McLeod.Despite the obstacles, authorities from at least seven neighboring counties have followed countless tips in their hunt for Decker, with some leads running hot.NATIONAL GUARD DEPLOYED IN MANHUNT FOR SURVIVALIST ACCUSED OF KILLING HIS THREE YOUNG DAUGHTERS"We had some break-ins and some items missing from campsites," Morrison said. "Nothing came of them, but were still following any leads that come in."However, the number of tips has reportedly dwindled as leads turn cold. Additionally, officers have started using cadaver dogs to search for Decker, the department previously confirmed to Fox News Digital."Clearly its looking more like the probability hes deceased," Morrison told USA Today. "Does he have the potential of surviving out there? Yes. But with the amount of people out there with no signs whatsoever its not likely. Its possible, but for now were presuming he is still alive."US MARSHALS ESCALATE MANHUNT FOR FUGITIVE DAD WANTED IN DAUGHTERS' MURDERSThe U.S. Marshals Service remains the lead agency in the four-week-long hunt, working alongside SWAT teams and local law enforcement."You have to be responsible with your financial resources," Morrison said. "Which means you have to ask whether you are tracking active leads. Typically, people who disappear want to live in more populated areas where they have access to supplies."At the time of the girls deaths, Decker was homeless, living between motels and campground sites while suffering from mental health issues, according to court documents. He is charged with three counts of aggravated first-degree murder and kidnapping.The Chelan County Sheriff's Office did not immediately respond to Fox News Digital's request for comment.Decker is described as a white man standing 5 feet, 8 inches tall, and weighing approximately 190 pounds.Authorities warn that he is considered armed and dangerous but insist they have no reason to believe Decker is a threat to public safety.The U.S. Marshals Service is offering a $20,000 reward for any information leading to Deckers arrest.