Four people were killed in a shooting at a bar in Anaconda, Montana, on Friday, authorities said. A suspect is at large.

Montana Gov. Greg Gianforte on Tuesday signed an executive order freeing up more resources for local law enforcement as they searched a mountainous area for a former U.S. soldier suspected of killing four people at a bar last week.

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.