What is the proper way to hold a knife when stabbing?

Here we have Google Boy and Shortie (not to be confused with Shorty) demonstrating two different angles to hold a knife when stabbing someone. Notice the tip of the blade in photo 1 and how the tip of the blade is reversed in photo 2.

At first I would have thought photo 2 is correct but the more we looked at it photo 1 seems correct.

Upon further discussion we have decided it depends on the damage to be inflicted. For numerous stab wounds photo 1 would be the proper blade angle. To really slice someone up photo 2 seems to be the proper blade angle.

How would you hold the blade?

Happy Halloween