The former U.S. Army soldier accused of gunning down four people at a Montana bar has been captured following a weeklong manhunt.

Experts on mass shootings said it’s rare for the gunmen who carry out such crimes to elude the authorities for so long.

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.