Police have found the getaway car of a US military veteran who walked into a bar in the western state of Montana on Friday morning and fatally shot four people, but the gunman remains at large.

ABC News contributor and former NYPD chief Robert Boyce breaks down the ongoing police investigation after a gunman opened fire at a Montana bar, killing at least four people.

Investigators are piecing together more details about how a former high school football player who blamed the game for his mental health problems carried out a deadly attack on an office building that ...