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

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.

A manhunt is intensifying for the gunman who allegedly killed a bartender and three patrons at a bar in southwestern Montana, authorities said.