If somebody is firing indiscriminately into a crowd you'll be safer pressed to the ground where you won't get hit by a bullet flying through the air randomly. If there is something to get behind quickly that would be the better option. Yes, if the shooter is specifically aiming at you they can hit you easily if you are stationary on the ground. If, God forbid, there was ever a shooting in the middle of MK, it's more likely somebody is just going to open fire into a crowd and fire until security and the police (hopefully quickly) take them down.