Some of the four people killed in a deadly Alabama shooting had "extensive criminal" histories and might have been killed in a "cowardly" murder-for-hire hit, authorities said Monday.

Alabama officials are asking for the public's help in a manhunt for the shooters they say killed four people and injured 17 others in Birmingham. The reward is up to $100,000 for information leading to the suspects' arrests after they allegedly tried to pull off a murder-for-hire but hit many innocent bystanders.