Former police officer's hero instincts kick in during Sydney Airport arrest

When there's a commotion and someone needs help, many people wonder if they would jump in as the hero or freeze.

For former police officer William, his instincts kicked in.

When he saw two Australian Federal Police officers struggling to arrest a man at the airport this morning, he and his off-duty police officer friend jumped in to restrain the man.

And then a gun went off.

Watch the full story in the video player above.