Mysterious Shadow From GoPro 60fps Footage -- Can You Explain This?

So while editing the previous episode of The Tom E Gunn Show (Shooting Crackers) I noticed something extremely curious that raised my eyebrows a bit.

There are 3 frames that inspired this frame by frame break down, which I shall call Frame 1 2 and 3.

Frame 1 is the before impact footage.
Frame 2 is milliseconds before the impact, so close that you can see the .30-06 bullet clearly in the frame.
Frame 3 is milliseconds after the impact, where you can see the crackers exploding.

Now what I noticed was that between Frame 1 and 2 the shadow of the crackers changes dramatically, but the crackers stay the same.  And then between Frame 2 and 3 the crackers explode, but the shadow stays the exact same...  So it's like the shadow from Frame 3 has bridged backwards to Frame 2.

Why can you see the bullet before impact and a shadow resulting after impact in the same frame of footage?

If anyone knows the answer to this please let me know because I would like to know!  It makes no sense to me...