the unexpected demise of signature bank over the weekend along with the failure of silicon valley bank on friday ignited a shootfirstaskquestionslater reaction among regionalbank investors as customers moved deposits to the largest us banks for perceived safekeeping observers said monday stocks of regional banks such as first republic bank frc western alliance bancorp wal pacwest bancorp pacw and zions bancorp zion dropped monday even after us bank regulators set up a new emergencyloan program as a backstop