Your scenario per the Reddit "gray Nissan FLA. Tags" is plausible but then I speculated maybe Person #2 (or other) moved the vehicle say to Ives where the last known red line sighting sits alone on the Providence Police released map.The 'after' sightings make me doubt the reddit tip somewhat. If his car was really parked where they say it was, then he would have had to circle back around to get to it. And that should have put him on some of the cameras that captured him before the shooting. But LE apparently doesn't see him on any of those cameras after the shooting.
It has been discussed prior in here, and that is the lead LE needs (and all of WS'ers) is a good video of a vehicle/moped/ebike of how the POI arrived or left the area between Waterman, Ives or any other street. jmo