Given that the bridge is covered in high suicide barriers and CCTV, if the intention was to throw the suitcases off the bridge then I can only assume the person didn't know the area very well, or is seriously mentally ill.
Or just really was a poor planner.
I still can't get over that one murderer who threw a bag of stuff associated with a crime off the local bridge in the dead of night.
He'd failed to take into account that it was the dead of winter, and the waterway was mostly frozen over around the pylons.
Nothing he could do.
When dawn broke, the bag was almost immediately spotted, sitting neatly on the ice, by a passerby.
The bag was retrieved without any issues by police, was found to be wonderful evidence, and away to jail he went.
Even if someone plans the crime itself, they often don't plan the aftermath.
Evelyn Colon and her baby were also disposed of in multiple suitcases from a high bridge. They landed not in the water, but on the bank, where they were found in short order. She had to wait for genetic genealogy for an identification, but once she was identified, they immediately knew who the culprit was and arrested him.
Aydil Fontes was also disposed of in suitcases in a waterway... Problem was, there was no current. So the killer came back several days in a row, only to see the suitcases floating right around where he'd thrown them in, but just far enough out to not be able to be retrieved by him. His suspicious behaviour was reported by local residents, and to jail he went.
Tl;dr, people who use dismemberment and suitcases and waterways/bridges for inconvenient human remains often haven't thought it through beyond getting those remains away from them. They tend to be acting very reactively. And I can absolutely see someone being thwarted by anti suicide barriers and CCTV, and then having nothing to do but wait for the inevitable knock at the door.
MOO