Security footage from the building captured the slaughter, including the moment that Tamura turned his gun on himself, and police have already identified the suspected shooter as 27-year-old Shane Devon Tamura of Las Vegas.

Security footage shows the shooter leaving a black BMW that was double parked on Park Avenue with an M4 rifle before to the attack, according to NYC Police Commissioner Jessica S. Tisch.

The NFL’s headquarters, Rudin Management, KPMG, Blackstone Inc., and a number of prestigious law firms are all located in the building where the incident took place. Tamura killed someone else and then himself after taking the elevator to a floor.

The investigation is still underway, officials told NBC News, adding that while a motive has not yet been revealed, they are investigating a message left by the suspect.

In the meantime, a source familiar with the investigation