It's interesting that he held the lease on Tanya's apartment. He seems to have had power over her. She trusted the wrong person. She trusted him enough still that they were intimate not long before she died, it appears. Unless-a remote possibility-it was after her death, or even not consensual.
I wonder how he ended Tanya's lease/tenancy without raising any red flags. And he had to dispose of everything in her apartment himself.. I wonder how he managed that. He knew, of course, her family wouldn't be trying to reach her, or at least not for sometime as they were largely estranged. So that's one concern he didn't have. In the photos of his most recent court appearance, he looks slightly in disbelief he was ever caught in my opinion.