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.

Officers are "unrelenting in their pursuit, working around the clock" to find him, Montana Gov. Greg Gianforte stressed at a news conference on Tuesday. "Rest assured, our brave men and women of law enforcement aren’t giving up."

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