My first inclination was a perp who is obsessed or angry with Carlesha and very determined to take her. Someone she knows -- or maybe someone who has been quietly stalking her. A sexual or power motive, based on the preplanning, determination and violence level.
But now, from the second video, I'm wondering if it was a robbery motive like her parents mentioned. It looked to me like she was trying to avoid him, as you would a stranger in the dark -- then suddenly stops and faces him. I'm wondering if he called her name "Hey, Carlesha!" so she stopped and turned. He stuck out his hand, "Remember me? From _____?" so she reaches to shake his hand. Their interaction feels like he's a friend of a friend, maybe an acquaintance she only met once. Then he doesn't let go and she realizes she's in trouble and begins to fight. So frightening.
I am guessing Carlesha had a decent amount of money in her account. Maybe she had been saving up for something and had mentioned this to others. It seems to me, if this was a robbery, it wouldn't be worth all this preplanning, etc. unless he expected to get a lot of money (and would therefore need her cooperation, her PIN number). From how far away he parked and where he grabbed her, I believe the perp assumed that with a knife or gun as a motivator, he could easily get her to walk with him and get in his car, then drive her to an ATM, where she would give him her PIN out of fear. But he was wrong about Carlesha. She's a fighter. He ended up having to get very violent with her to get her in the car.
The smile at the ATM makes me think he was looking at the balance of her account and had either been able to access it, or was expecting to shortly. He seems very comfortable with these various hardcore criminal actions -- very cocky. He seems to have no anxiety, doesn't seem to look around for witnesses or cameras. This is my current read on the situation... but I am riveted to find out what really happened to poor Carlesha. She fought so valiantly! I sure hope the man who did this to her is caught and taken off the streets forever.