While the FBI Agent is searching the woods near the house after hearing a sound Theo sneaks up and kills the Agent. The ground is covered in leaves making it near impossible for Theo to have snuck up on the Agent without him hearing.
While Agent Hardy is making his escape he manages to disable one of his captors and take his gun (1911). Agent Hardy then racks the slide to load the gun and gets into a firefight shooting at least 12 rounds. 1911's have a max capacity of 8 rounds using a standard size magazine therefore could not could not have fired the 12 rounds. I should also note that the 1911 in addition to the 8 rounds in the magazine can carry one round in the barrel making it 8+1 for a total of 9 rounds however we can assume there wasn't anything in the barrel since Agent Hardy racked the slide to load it.