The mental health of suspected Montana gunman Michael Paul Brown, 45, declined significantly following the death of his mother, relatives said.

The suspect accused of fatally shooting four people at a Montana bar and who remains at large struggled with mental health issues, but was denied services from agencies that were supposed to help, according to his niece.

Stymied by treacherous terrain and untamed wilderness, authorities are struggling to find an Army veteran suspected of killing four people at a Montana bar last week.