To the left in the photo is another man with an almost identical back pack. And if you had access to all video and photographic evidence you could see no telling how many people cross that path with backpacks. And since these are two photos of the same place just seconds apart then that would indicate that they were cut from video so why not show the video that they were clipped from so we can see him drop the bag? That would be proof.
In this world of constant surveillance where they can rewind time and pick and choose who they want to pin something on or set someone up then they can make anyone look guilty as sin just for being in the wrong place at the right time. It's like saying that YOU are planning to make a bomb just because you have everything needed to make a bomb in your house or apartment right now. So you are guilty.
Is this guy and his brother guilty of participating in this crime? Maybe but until I hear of some logical motive then nothing is proven because images can be picked out of context or even edited to sway opinion.