Yeah it look like the pellet fragmented but more than likely that was part of him exiting. Not side shot but my own build known as the Hajimoto Scope Cam Assembly (HSCA). I share its build evolution and development in two videos that can be viewed here:
Original Build Video https://www.youtube.com/watch?v=jwOLKC0iAuo
Follow up video which introduces an IR night vision element https://www.youtube.com/watch?v=8APRELdP36Q
Image captured using the HSCA with GoPro Hero 4 Black in 720p@240FPS edited in Adobe Elements and Premier.