Either they wanted us to think Thomasin attacked first so they can sell us some self-defense sob story, or... it's to try to distract us from something. Like how if Thomasin was fully covered in paint, that puts them in the splash zone too.

But here's the tricky thing with that: how do you cover someone in paint, kill them, and then not leave footprints? so the paint would have to be somewhere else if they got any on them.