I felt the bldg shake. I left Sirius in his kennel & responded to the mezzanine of #1 WTC to assist people coming out of the "A" stairwell. I saw bodies falling onto the Plaza & realized that I was needed on the upper floors. I proceeded up the stars giving encouragement & calming the fears of the people coming down. Those that were seriously injured I assigned to healthy personnel, directing them to the triage area. On the 27th floor, I met a man in a wheelchair with a friend. They were waiting for the crowd to clear before attempting a descent. I left them with FDNY personnel & proceeded up the "B" stairwell. This switch of stairwells later proved to be my lifesaving decision. Upon my arrival on the 44th floor, I started evacuating those on the floor towards my stairway. I heard an explosion & as I looked to my left, a fireball blew out the windows, knocking us to the ground. I knew now that we were under attack & proceeded down the stairway with my people. On the way down, we cleared floors of any remaining employees.

They continued to ascend to the 39th floor. This is as far as William got before he was turned back by the firefighters. As he began his descent he heard the plane hit the south tower.

because it was now the closest
stairwell to get up. While I was there, there were still people coming down,
somewhat confused, because there were stoppages from people trying to
come by. But I just kept on telling everybody, “Down is good, keep going
down.” Because they were concerned when they saw me going up.
So right away they think, “Well he’s going up, why are we going down?” And
I remember getting up to the forty-fourth floor just as Tower Two got hit.
And the concussion knocked me to the ground and blew out some windows.

That’s when I realized that it was no longer an accident. Before that point,
most of us had felt that even though we knew it was an airplane, we couldn’t
conceive of the idea that it was done on purpose, even though it was a very
clear day