Sheriff Glenn Huestis confirmed to The Havre Daily News that Pat Pyette died, but it was not immediately clear when. The undersheriff was 54.
The Montana Highway Patrol initially reported that a deputy was outside his vehicle directing traffic Wednesday evening between Chinook and Harlem when he was struck by a westbound vehicle. Patrol dispatchers in Helena would not release details on Thursday.
Pyette was praised by the sheriff, who called him "a fine man, willing to do anything for anybody, no matter who or what. He was dedicated to our community and the people he served."
Blaine County Commissioner Vic Miller said the death will be felt by anyone who knew him.
"I don't know anybody that didn't respect him and like him, and given his line of work, that's a rare characteristic," Miller told the Havre newspaper. "He was the kind of guy you want to have for a friend and neighbor."