Firefighters from the New York City Fire Department rushed to the World Trade Center minutes after the first plane struck the north tower. Chief Joseph Pfeifer and his crew with Battalion 1 were among the first on the scene. At 8:50 a.m., an Incident Command Post was established in the lobby of the North Tower. By 9:00 a.m., shortly before United Airlines Flight 175 hit the South Tower, the FDNY chief had arrived and took over command of the response operations. Due to falling debris and safety concerns, he moved the incident command center to a spot located across West Street, but numerous fire chiefs remained in the lobby which continued to serve as an operations post where alarms, elevators, communications systems, and other equipment were operated. The initial response by the FDNY was on rescue and evacuation of building occupants, which involved sending firefighters up to assist people that were trapped in elevators and elsewhere. Firefighters were also required to ensure all floors were completely evacuated.