Stymied by treacherous terrain and untamed wilderness, authorities are struggling to find an Army veteran suspected of killing four people at a Montana bar. But the difficult landscape isn’t the only challenge.

Police are looking for Michael Paul Brown, 45, after four people were shot and killed in The Owl Bar in the small town of Anaconda, Montana.

On Monday, the U.S. Marshal Service posted on X that a reward of up to $10,000 would be offered for any information leading to Brown. The agency has also set up a tipline at: 1-8-77-WANTED-2.