What Happened to the Overturned Car?

Officers Amora then drove towards the scene, and as he did so, he radioed the sheriff's office telling them he had a possible 1044 or accident. He then got out of his police vehicle to check on the overturned car. At this point he heard two or three thumping sounds like someone hammering or shutting a door hard. It started low in pitch and then rose in frequency as well as getting louder. The only time I saw these two persons was when I had stopped for possibly two seconds or so to glance at the object. These persons appeared normal in shape, but possibly they were small adults or large kids.