The latest happened Monday at a Bank of America in Oxnard.
According to the FBI, the bandits were extremely violent and assaulted employees inside the branch.
Surveillance photos show two men seen inside the bank prior to the robbery. Federal agents say these men aren't considered suspects but may have information about the robbery.
Another bank robbery happened back in July at a Bank of America in Oak Brook. Witnesses say four armed men burst into the branch with guns and ordered customers and employees to comply with their demands. The suspects then robbed the bank and in some cases stole the victims' personal belongings.
Bank of America is offering a $10,000 reward for information leading to the arrest and conviction of the persons responsible for these four armed bank robberies.