I would like to point out that when Henrietta snipes the two guards in the front of the mansion you can hear the gun fire ...slight pause... and then the bullet wizzing by to b~tchslap the guys brain onto the wall behind him.
When standing that close to the target, it would be the opposite. His head would fly before you heard anything. Even when standing next to a high power rifle and watching a target 100 yards off the bullet striking it's target and the sound would be almost simultaneous.

*sigh* , but alas, it is
cooler when animated like it was. Some people would probably complain that their audio was off if they heard the gunfire afterwards -_- ...
P.S. if I remember correctly since i am too lazy to look it up and I have to get going soon: sound travels at about 1300 ft per second at sea level and an AK-47's bullet usually travels around 2800 ft per second? PLEASE correct me if I am wrong, which I probably am.