More than likely, it would've been dismantled in a mirror-image process to its construction. Roof-mounted cranes would lower removed structure down the side of the tower, then the cranes would lower themselves to a lower floor. Repeat until the stub of the tower is short enough to finish off with ground-based cranes.
Trying a controlled demolition drop on something that tall, that's already sustained major structural damage, is going to be very dangerous, and time-consuming to boot. In fact, given my understanding of how the towers were structured, by the time you stripped out the structure to prepare it for a controlled drop, you'd already have the vast majority of the demolition/dismantling done anyway.
Disclaimer - Not a structural engineer, nor do I play one on television. I didn't even sleep at a Holiday Inn Express last night.