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

A manhunt for Michael Paul Brown has been underway since Friday morning, when four people were shot and killed in the town of Anaconda.

The search for a former U.S. soldier suspected of killing four people at a bar in Montana stretched into a fourth day Monday, with deputies scouring the mountainous terrain by foot and air after the man escaped in a stolen vehicle containing camping gear.