Speculating and thinking aloud...
Suppose Doorway Guy was checking HG out and wanted to approach her. Dreadlocks Guy thwarts Doorway Guy's plans, but only for a moment. HG shakes off Dreadlocks Guy and when she is alone again, and Doorway Guy makes his move.
The fact that Doorway Guy didn't come forward until Wednesday night when the video was about to be released bothers me. If he were truly a concerned citizen, I would think he would have come forward as soon as pictures of HG were made public. It also bothers me that the bloodhounds found a scent at the parking lot. Doorway Guy looks like someone who would've driven to the mall.
When did HG turn back for a second? Could Doorway Guy have said something to her?
Doorway Guy describes someone different than Dreadlocks Guy because he knows Dreadlocks Guy is innocent, but perhaps seeing Dreads talk to HG put the idea in his head to name a black man. He has to come forward because the video will be public - someone will recognize him - and he has to put the blame on someone so he makes up a description.
All speculation, not based on anything reported. I could be way off base, and reserve the right to change my mind.