This is bullshit. The actual owner has the deed in his name.
I’d kick this guys ass down the road a few miles. Or call the cops as someone breaking and entering.
I know, in a situation like this, if someone shows court paperwork to the effect that he has a right to the house - then the cops are going to defer to the courts and tell all parties to “work it out in court”.
I’ve been in enough situations, which are not exactly like this, but in which there is “legal paperwork” which shows different than someone else is claiming. The cops are not going to act on that. The courts will have to act on that.