I agree that they may have already found YZ, and they are determining all sorts of things about his crime against her.
But also:
*based on his brazenness to take a female midday,
*using his own car,
*returning her to his apartment and have no screaming be heard,
*then moving her,
*his behavior since June 12 when the FBI first made contact with him, and especially
*his smug stroll, bragging, and planning of future victims at the vigil;
I have a gut feeling Yingying is not his first victim. I think he went to fetlife to find someone but it was too slow or he realized it was not real enough for him - so he just went out and took someone. I think the FBI needs to investigate into all unsolved young females gone missing within the past 1-2 years. And I think his car and apartment has some DNA of more than one female that they need to examine before releasing any further information. By looking at his mugshot, I feel absolute terror and sadness on behalf of Yingying. He was crazed and determined, and she had no chance.
Contrary to what others might think, I don't think he was sloppy at all. He cleaned up real good. But... not good enough. And I think that's what's going on behind the scenes. jmo