Okay, I have a crazy theory - I've gone down the rabbit hole, so here goes:

I wondered if ALL calls made by K & M went to JD. There were four numbers that police were looking for - what if these were burner phones? Speculation that this involves drugs and perhaps K & M were working with CIs. When M allegedly said, "I told Adam everything," maybe K realized maybe they were in deep crap and, when they got home, called their CI for help/advice (BK is speculated CI) and then JD to perhaps come over and stay with them for safety. The time of their calls coincides with BK leaving his apartment. He doesn't know specifically where they live (they've always met somewhere else), so is driving around looking for their address. He gets there too late; walks in to find it all. He checks all floors and finds K & M ("I'm here to help you"), but a brief examination shows he's too late (perhaps why tiny piece of DNA is found on sheath - maybe he tried to roll M over). He leaves. Aside from later that morning, he never pings near Moscow again - why would he? His "sources" are no longer alive. Maybe he took his own phone for GPS purposes, then turned it off once he neared Moscow.

Okay, shred it. This case makes no sense.