A thief with a weapon, especially one belonging to a group that attacks people travelling through the countryside. (Cambridge Dictionary)
Robbers are sometimes called bandits, especially if they are found in areas where the rule of law has broken down. (Collins Dictionary)
A robber or outlaw belonging to a gang and typically operating in an isolated or lawless area. (Oxford Dictionaries)
An outlaw who lives by plunder. (Merriam – Webster)
Cowboy Bandit. Vector Stock.