Roughly 3735mph would be good enough to kill via thermal energy at atmospheric pressure. At that point you'd hit them effectively a superheated plasma round that was, formerly, your genitals. The sonic boom itself might generate a strong enough kinetic force.

If you want to do it with blunt kinetic force you will need to do it in a vacuum, as the structure of your weapon if simply not stable enough to apply that much kinetic force before tearing itself apart on air resistance.

Calculations performed thanks to the "slap cooked chicken" theory, which she used as a basis for her math.