JACKSON, Wyo. (AP) — Authorities say a 33-year-old man is dead after he apparently hit a tree while snowmobiling in northwest Wyoming.

Andrew Grossnickle, of West Fargo, North Dakota, was snowmobiling with a group of friends west of the Togwotee Mountain Lodge on Friday morning when he somehow became separated from the vehicle and hit a tree.

One of Grossnickle's friends came upon the scene and performed CPR, but Grossnickle was pronounced dead about half an hour later. No one saw the crash, and it's unclear how he became separated from his snowmobile, which was not damaged.

The cause of death is still undetermined, and an autopsy is planned for Saturday.

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