Triangle Face a bounty hunter was tacking Dr Evanzen and Walrus Man before Jyn Bumps in to them…
This probably allows the two criminals to escape as Triangle face is caught the other side of the Hover Tank and has to wait then the battle kicks off allowing Dr Evanzan and walrus face to evade capture.
He may have been going to shoot just as Jyn bumps in to them or does he bump in to Jyn to cause a diversion.
This is a thread where we try to figure out what was originally shot, not make things up. Where are you even getting this stuff?
Some of it is in the Rogue One Visual Dictionary, and some of it is pure speculation.