JOSHUA TREE — An autopsy released Tuesday doesn’t answer the mystery behind a murder-suicide at Joshua Tree last year, but it does provide some hints about how the young couple’s trip unfolded.

The decomposed remains of Joseph Orbeso, 21, of Lakewood and Rachel Nguyen, 20, of Westminster were found Oct. 15 in a secluded area under a tree, nearly three months after they went missing at the park.

Sheriff’s detectives contend that Orbeso shot Nguyen, whom he had previously dated, with a .40-caliber handgun and then turned the weapon on himself.

Friends and Orbeso family members have said they believe the murder-suicide was a result of desperation, not anger, and that the shooting happened only after the couple became lost in the sprawling park and ran out of food and water.

The autopsy offers nothing to support or contradict that belief. It does note that the couple’s remains were found only about 2 miles from where they had parked their car, a fact that might suggest confusion.

“Since we don’t have any evidence to tell us why the shooting occurred, we are left to speculate,” Jodi Miller, spokeswoman for the San Bernardino County Sheriff’s Department, wrote in a prepared statement.

“Knowing that they rationed food, had no water, and were seeking shade certainly sheds light on the apparent dire circumstances.”

However, the autopsy and an accompanying investigative report do offer a few glimpses into Orbeso and Nguyen’s odyssey.

Detectives learned the couple obtained hallucinogenic drugs prior to entering the park and they found an apparent hallucinogenic mushroom in a backpack under Orbeso’s body. But it’s unclear if drugs played any role in their deaths.

The toxicology test did not reveal any drugs in Orbeso’s system at the time of death. A separate test on Nguyen found trace elements of cannabis in her system, and detectives found two round plastic containers that have might been used to store marijuana, a drug she had a medical license to consume.

The report did note that the couple were inexperienced hikers and investigators couldn’t determine what type of survival equipment they had.

Orbeso and Nguyen were last seen July 27 when they left an Airbnb rental near Joshua Tree to go hiking.

Authorities were alerted the following day when it was determined they hadn’t checked out. Clothing, an iPad and food were found in their room. Nguyen’s maroon Lexus, along with fresh footprints, were discovered near Joshua Tree’s Maze Loop.

For several weeks, searchers scoured various sections of the park but were unable to find the couple.

Then on Oct. 15, searchers looked at an area that had not been thoroughly investigated. At the base of a dried waterfall they found two water bottles, along with a pair of spent .40-caliber cartridge casings, according to the investigative report.

Continuing east, the searchers discovered more items — an e-cigarette holder, a pocket square, two black sneakers and a partially empty bag of beef jerky.

“These items were scattered throughout the wash, consistent with being taken by rain runoff,” the report says.

About 500 feet from where some of the items were found, searchers discovered the decomposing bodies of Orbeso and Nguyen. They were side by side, under a Cat’s Claw tree, against a canyon wall.

Detectives believe the couple might have been seeking shelter from the blazing sun.

“A tan-colored shirt was laid across the female’s legs,” the report says. “A black shirt was partially wrapped around the back of her head, as if used as a hat. The male’s shorts were unzipped and partially pulled down to his thighs, which appeared consistent with trying to cover the lower legs from exposure to the sun.”

Nguyen’s left arm was extended under the remains of Orbeso. Orbeso’s right arm was resting on Nguyen’s left hip.

A Band-Aid was found on Nguyen’s right knee covering a half-inch cut that did not appear debilitating.

In addition, a.40-caliber Magnum revolver containing three spent cartridge casings in the cylinder and three empty chambers was found buried in the sand next to Orbeso’s left leg.

While Orbeso and Nguyen each died from a single gunshot to the head, it hasn’t been determined if the third shot might have been fired to gain the attention of searchers, Miller said.

Family members for Orbeso and Nguyen could not be reached for comment.