Boston police and fire responded to 50 Terminal St. in Charlestown this morning after a passerby around 9 a.m. noticed a car in the water.
Fire Chief Steve Dunbar said that a and found it empty.
The car must have come down the ramp "with some force," he said, but may have floated further away from the ramp overnight.
One tow truck tried to remove the vehicle, Dunbar said, but wasn't large enough to do the job. A larger tow truck arrived around 10 a.m. and around 10:30 a.m.
The chief also found a spent shotgun shell at the scene.
At 8:37 a.m. Tuesday, Stoneham Police received a report of a 2005 white Nissan Ultima that was stolen from 122 Main St., according to Lt. Jim McIntyre. He added that the vehicle went missing sometime between Monday afternoon and Tuesday morning.
A Charlestown resident at the scene said that the quickness of the emergency response surprised him. When he woke up and looked out the window, he said, he didn't see any signs of emergency crews. Just 15 minutes later, he said, the area was suddenly filled with fire trucks.