Sheirer, 65, of Staten Island, became known as "the man behind the mayor" during Mayor Rudy Giuliani's daily briefings on the 9/11 rescue and recovery efforts.
The agency's offices were destroyed at 7 World Trade Center but Sheirer rallied his workers -- first at a nearby firehouse, then the police academy and later Pier 92.
In those months of fear and uncertainty, city officials said it was Sheirer's idea to have "one message, one voice." Everything from the death toll to alternate-side parking rules was delivered through Giuliani to give the public a sense of continuity.
Even as Sheirer learned of the deaths of his firefighter friends, the former fire department dispatcher saw to the needs of foreign families looking for relatives, widowers, Ground Zero debris-removal crews and more.
"He had the hardness of ice but none of the coldness," said David Longshore, an agency spokesman who worked under Sheirer.
Giuliani issued a statement Thursday hailing Sheirer as a hero.
"He guided the most extensive relief and recovery effort ever. It was done with great skill and sensitivity," Giuliani wrote.
In June, the New York State Legislature honored Sheirer's 9/11 work with a resolution.
Thursday morning, Sheirer was driving to his job as senior vice president at Giuliani Partners, a consulting firm, when he suddenly felt sick. He pulled over and called 911, said Guy Molinari, a friend and former Staten Island borough president.
The Brooklyn native graduated from St. Francis College in Brooklyn Heights and worked for the city for more than 30 years, 20 of them at the fire department. He was named deputy fire commissioner in 1994, and became deputy police commissioner two years later.
Christopher Sheirer, of Staten Island, said his father was a "simple man" at heart. "He would always drop everything to help people," he said.
Visiting hours are 2-4 p.m. and 7-9 p.m. Saturday at the Frank E. Campbell funeral home in Manhattan and the service is 11 a.m. Sunday at Temple Emanu-El in Manhattan.