The lieutenant who never returned from his backcountry trek on the Sierra High Route near Independence, California, on Feb. 23 was likely dead, the Marine Corps said Thursday.

Lt. Matthew Kraft, 24, a member of the 1st Marine Division in Twentynine Palms, was scheduled to end his trip 130 miles north near Bridgeport, California, by March 4 or 5, but never turned up. When Kraft’s father didn’t hear from his son, Mono County Sheriff's Office initiated a search March 4.

“Given the timeline of events, severe weather, and increased avalanche activity in the search area, on-scene search and rescue experts have determined that Kraft was most likely overcome by severe weather and exposure,” Capt. Paul Gainey, spokesman for the 1st Marine Division told the Orange County Register. “The Marine Corps will continue to stand by and support Kraft’s family, friends, and Marines during this difficult time.”

“All the Marines in 1st Lt. Matthew Kraft’s chain of command grieve with his family. We are heartbroken for the family and friends of 1st Lt. Kraft, and the command will do everything they can to help the family and friends of 1st Lt. Kraft,” Gainey added.

Among the agencies who joined in the search and rescue of the marine were the California Highway Patrol, the California Office of Emergency Services, Yosemite National Park, Sequoia and Kings National Park, Madera County Sheriff’s Office and the Marine Corps Mountain Warfare Training Center. In addition to other equipment, an all-terrain vehicle equipped for wintery climes known as a “Snowcat” was deployed "to rope-tow search and rescue team members on skis up to the Onion Valley parking area" near where Kraft's empty vehicle was found.

Initially, responders said they hoped to reach Kraft before the onset of a winter storm in the area. However, in March, authorities said they found avalanche debris. As April rolled in, Carma Roper, spokeswoman for the Inyo County Sheriff’s department, said they would continue to follow up on leads such as the discovery of a backpack, tent or other personal effects.

“The search area is massive and the backcountry snowpack in the Sierra is still very heavy,” she said.

Since Kraft had survival training, Gainey said last month he and his fellow marines had high hopes that Kraft was still alive and surviving in the California wilderness.

“We’re optimistic he has all the tools he needs to survive,” Gainey said. “Anytime a Marine takes liberty we make sure he has a plan. He communicated his itinerary and the gear he had. He also gave us information on his drop-off and pick-up point.”

Kraft had begun his solo ski trip after notifying family and the Marine Corps in advance. The 195-mile trek along the Sierra High Route was filled with elevations along the route, ranging from 9,000 to 11,500 feet. The trip was to be completed in 10 days.

U.S. Marine Corps
In this photo, U.S. Marines prepare to march in the Veterans Day Parade on Nov. 11, 2017, in New York City. Getty Images/Spencer Platt