I have to say that if the man is a Bristol resident, it is a seriously bizarre place to dump the cases like that on the bridge. Everyone in Bristol (I lived there for years and my direct family still do, and live in Clifton) knows that the suspension bridge was a hotspot for suicides and is covered with high fences, security and CCTV and is a popular spot for people to go and visit, even at night for the views over Bristol, or sitting on the green nearby.
If he went thinking he would be able to dump the cases over the bridge into the water, it makes me think it could be someone from outside the Bristol area. It only takes about 5 minutes to walk down a path from the suspension bridge right to the river bank, in a much less populated and camera-covered area, where he would have been able to dispose of the cases without half as much interaction.
However if it is someone from outside of Bristol - why on earth would you travel into the city to dispose of remains like that? Also doesn't make sense.
The logic of the decision baffles me. Leigh Woods where they are searching now is also a known hiding spot.
I hope this is not connected to the young lad that went missing a few months ago.