Complex sentence: As a group had gathered to watch the argument the other gang members would pickpocket the crowd where they would meet back at their headquarters on Forsyth Street on Manhattan's Lower East Side to divide up the money.
Split into simpler sentences: As a group had gathered to watch the argument the other gang members would pickpocket the crowd. Then they would meet back at their headquarters on Forsyth Street on Manhattan's Lower East Side to divide up the money.