We, just for the sake of supposing, if round was barely supersonic- 155 grs at 1100 fps is 416 ft lbs. Assuming it lost half its energy on the bounce, that would have be 208 ft ft lbs. And yes, that is definitely enough to be fatal.
Working from the other end- a 5-6mm gouge in concrete would equate to a bullet penetrating several inches into your skull. Minimum compressive strength of sidewalk grade concrete is about 3000 lbs/sq inch. Compressive strength of human skull a few hundred lbs/ sq inch.
What we have heah is.... failure to communicate.