There have been a lot of good suggestions for this loud thud. Imo, if LE did not equate the thud to the crime, I do not think it would have been included in the arrest PCA. The paragraph about this thud was placed right in the middle of DM's account of hearing crying and talking in X's room, and then her seeing the man in black walking towards the exit. I feel like that paragraph placement was not haphazard. If LE thought the thud was the sliding door, or the killer slamming the trunk or car door, or some other random neighborhood sound, why not put it after the paragraph about DM seeing the man in black walking toward the exit? Then it would support him leaving the house at 4:17 and driving off at 4:20, as seen on camera.
Instead, as the PCA is written, we have DM hearing crying and talking. We have camera audio, specified as less than 50 feet from X's wall, pick up whimpering or voices. We have a loud thud, then DM sees the man walking towards the exit. Imo, it seems the PCA is laying out the timeline of events from when DM woke up to when the car was seen leaving the scene.
Just because the PCA does not include anything about DM hearing a thud or barking doesn't necessarily mean she didn't report those things. Maybe the camera picking that up was more reliable info to add to the PCA because it had the specific 4:17 time stamp, which DM likely couldn't relay. Idk...