It's funny because real life is not the movies and lots of diffrent things happen when you shoot watery objects. You will see lots of skull and stuff coming out of the entrance wound with the higher velocity rounds.
Anyone who shoots prairie dogs has probably observed they flop on all diffrent directions also. Up and back has to be one of the weakest arguments that Oswald didn't fire the killing shot. Especially when the recovered bullets came from the rifle they found in the school book depository, where witnesses said they heard shots coming from and his prints were on the rifle and hair and fiber from the clothing he was wearing in the blanket the rifle was wrapped in.
I shot a coyote one time at a dead run from about 150 yards. All his brains came out the entrance wound and were sitting on the ground where is summersalts started.
If you really want to know who killed Kennedy I van tell you. Lee Harvey Oswald. You're welcome.