That's quite a narrow parabola.
I suppose the bullet maintains alot of its rotational velocity on its way back down. Even though it stopped upward movement at one point, It sounds like it didn't tumble- remained ballistic? It's hard to imagine that kind of penetration at terminal V without the pointy end going in first.
Everyone's heard of it happening but what are the odds?
(I'd be tempted to check the bullet against the gun or swab his melon for residue)