A degree of insider info would be needed to know where BT was staying the night prior to the corporate meeting. Also, how did the shooter know BT would arrive at the Hilton more than an hour prior to the 8 AM start? NYC is a very busy and crowded place even at 7 AM, yet the shooter recognized and picked out BT at a peculiarly well-timed moment. He (?she) must have known him better than most. So I am leaning toward disgruntled former [employee, girlfriend, girlfriend's husband, screwed-over business associate, etc].