Complex sentence: After the gang left, several letters came addressed to Frank Kirtley (Dillinger), J.C. Davies (Makley), and J.C. Evans (Pierpont) but ss the gang left no forwarding addresses, the letters were returned to the postman.
Split into simpler sentences: After the gang left, several letters came addressed to Frank Kirtley (Dillinger), J.C. Davies (Makley), and J.C. Evans (Pierpont). As the gang left no forwarding addresses, the letters were returned to the postman.