FAIRPLAY, Colo. -- A young woman working in the San Isabel National Forest was found dead Tuesday night 10 hours after she radioed for help, screaming, "Help me! Help me!" officials said Wednesday.

A camper, who offered a ride to the woman's co-worker after the call for help came in, was later arrested in connection to the woman's death, said Vince Matthews, director of the Colorado Geological Survey.

The 24-year-old woman's death was immediately investigated as suspicious and as a possible homicide, Park County Sheriff Fred Wegener said Wednesday.

She was identified as Alyssa Heberton Morimoto from Denver, and was an intern for the Colorado Geological Survey.

Wegener held an afternoon news conference to discuss Morimoto's death and to announce an arrest in the case.

Wegener said the suspect was camping in the area, but said it is unclear if he was stalking Morimoto or if the killing was random. He added that while the man is being somewhat cooperative with investigators, they are having a difficult time identifying him because he has multiple aliases. Wegener said if the suspect is who they believe his is, then he is in his 40s and has a criminal record.

Morimoto was performing field survey work in a remote area of Park County Tuesday when she radioed her co-worker for help at 1:35 p.m. She was working with the service's Dr. Karen Houck, who is also a professor at the University of Colorado Denver. The two had gone up to map the area together but had become separated earlier in the day.

"She radioed at some point in time that she needed help and when her partner got back to the area where the vehicle was, she was no where to be found," Wegener said.

Houck told authorities that the two had made a plan to meet for lunch on the other side of the ridge. She said Morimoto took the Jeep and drove around to the other side of the ridge where she was supposed to meet up with Houck.

Houck said at some point she realized it was taking her longer to cross the ridge than first anticipated, so she radioed Morimoto to inform her. Morimoto said that was fine and that she would eat lunch without her, Matthews said. Houck said about five or six minutes later she received a radio call from Morimoto who was screaming, "Help me! Help me!" Houck said the radio then went dead.

Once Houck arrived at the Jeep she said Morimoto was gone and she didn't see the keys to the Jeep anywhere. Officials said at that point the suspect, who had been camping at a nearby campsite, came walking up the road and asked Houck what was going on. She told him what had happened and that she needed to get in cell phone range to call the sheriff's office, at which time he offered her a ride, officials said.

While Houck and the suspect were driving down the road, a district forest ranger was spotted driving up the road. They stopped him and were then able to radio the sheriff's office. The suspect was taken in for questioning and was later arrested in connection to Morimoto's death.

Searchers began looking for Morimoto in the Pony Springs area, near U.S. Highway 285 and Highway 24. That is southwest of Fairplay.

Searchers located her body at 11:38 p.m. on the west side of the forest road, Matthews said. The cause of death was not released but Wegener said they did recover a gun in the area, though he didn't know if the gun was used to kill Morimoto.

"I think we are extremely fortunate that this wasn't a double tragedy because the person who had given Karen the ride is now being held as a suspect in Alyssa's murder," Matthews said. "I'm grateful they ran into the forest service truck."

"I don't know what to think right now," Wegener said. "A young lady out there doing her job and all of a sudden she comes up missing. So, I don't know. There are a lot of unanswered questions."

Wegener said Morimoto was married.

"We're going to work hard to find out what happened," he said.

Investigators are waiting for autopsy results on the woman. The autopsy is scheduled for Thursday.

The Colorado Bureau of Investigation is assisting in the case.

The suspect in the case will be arraigned in Fairplay on first-degree murder charges either Wednesday evening or Thursday, officials said.

The executive director of the Colorado Department of National Resources, Harris Sherman, and Matthews, released a joint statement Wednesday evening.

"Our hearts go out to her family," they said. "It's a senseless tragedy. It ended the life of a wonderful young person."

Sherman and Matthews said Morimoto was a student at the University of Colorado Denver's campus and was working on a master's degree in environmental science.

They said she started working on a Colorado Geological Survey mapping project on June 1 for the summer with Houck. She was mapping geological hazards, including mudslides, faults and sinkholes from underground dissolving salts, Matthews said.

This was her second summer working with Houck, who recommended her for the job. Houck had taught Morimoto's first geology class, Matthews said. Before pursuing her graduate degree, Morimoto received her undergraduate degree from CU Denver and graduated with distinction. She was a high school graduate from the Denver Waldorf School and had been an exchange student in Germany.