A brigand is a bad guy, especially one who belongs to a band of armed robbers. Railway travel used to be dangerous in the days when brigands frequently robbed passing trains.
In the earliest years of the United States, travelers to the most sparsely inhabited parts of the country were vulnerable to highway robbers and brigands, groups of armed thieves who would stop stagecoaches and steal from those inside. The earliest kind of brigand wasn't an outlaw, however — he was a foot soldier in a legitimate army, from the Italian brigante, "trooper, skirmisher, or foot soldier." Brigand shares a root with brigade.