A man has been arrested in connection with the death of a 24-year-old geology student whose supervisor heard her scream for help on her radio before it went dead, authorities have reported.

The Rocky Mountain News identified the suspect as Robert R. Amos, 44, citing a source familiar with the case.

Alyssa Heberton Morimoto had been working in the Pike-San Isabel National Forest southwest of Denver with Karen Houck, a geology teacher at the Denver branch of the University of Colorado.

Authorities report the two had become separated by their duties, but remained in touch with global positioning system radios, and Houck suddenly heard the plea for help.

“She was screaming, ‘Help me, help me!’ and then the radio went dead,” Vince Matthews, the survey director, said about the call by the student.

Houck responded immediately to the GPS coordinates, but didn’t find Morimoto. Authorities reported her body was found about 10 hours later in a nearby area of the forest.

Park County sheriff Fred Wegener said a suspect was found with a rifle and was arrested on suspicion of murder.

“We’re still trying to figure out what all happened,” he told The Denver Post.

Authorities said during her frantic search, Houck encountered the suspect, who offered help. She got in his vehicle and started down the road, but Matthews said the district ranger arrived just then.

“Otherwise, I hate to think what might have happened to Karen,” Matthews said.

Morimoto was studying for her master’s degree and had teamed up with Houck on the mapping project.

Orders also have been issued for such crews to remain together in pairs. “I worry about lions and bears all the time with our mappers, but you just don’t think about this kind of evil,” Matthews said.

The suspect, being held on $800,000 bail, is scheduled to appear in court on Monday, according to sources for the Rocky Mountain News.

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