Complex sentence: Liesl shoots Ackerman in the back (although he is not injured due to his bulletproof vest); but one of Strom's men, Cruz (Pete Randall), discovers that the vault is empty.
Split into simpler sentences: Liesl shoots Ackerman in the back; although he is not injured due to his bulletproof vest. But moments later, one of Strom's men, Cruz (Pete Randall), discovers that the vault is empty.