FDNY Chief Joe Pfeifer was investigating a gas leak at the corner of Church and Lispenard Sts. when the first hijacked jetliner roared overhead and slammed into the north tower.He became the first person to utter the word "terrorism" on 9/11, and he was the first fire commander on the scene. The firefighters he sent up into the burning tower included his brother, Lt. Kevin Pfeifer. Kevin Pfeifer perished when the tower collapsed. Joe Pfeifer survived to become the FDNY's lead figure in preparing the department for future attacks."That's my job," he said simply. His efforts to increase awareness of the threat paid off on May 1, 2010, when the lieutenants from Engine 54 and Ladder 4 became the first to decide that what had been reported as a car fire was likely a car bomb.When this May 1 brought news that Osama Bin Laden had been killed, Pfeifer's response was to send a bulletin reminding every firehouse the war was not over."The threat environment is still a dangerous one," he noted Thursday.When President Obama visited the city Thursday to meet first responders and 9/11 families, Pfeifer qualified on both counts.He stayed on task at headquarters."Tons of work," he said.The firefighters on duty with Engine 54 and Ladder 4 went briefly out of service when Obama visited their firehouse, less because of the role the companies played in the car bombing than because of the 15 firefighters they lost on 9/11. Obama then headed to the 1st Precinct stationhouse to visit with cops from the NYPD and the Port Authority. The cops included Chief Thomas Purtell, who commanded the NYPD's search-and-rescue operations at the World Trade Center.He is the chief of Manhattan South and had not wanted to take even a few minutes from the effort to ensure Obama's visit went safely and smoothly.He did so only when ordered by Chief of Department Joseph Esposito, who felt a commander who was at the towers on 9/11 deserved to meet the President. Purtell immediately went back to work with the same unrelenting dedication shown by Pfeifer and so many others through nearly a decade of war. They would be first to say they wished the war were over, but also the first to say it is not.Obama said the same to the 9/11 families after he lay a wreath in memory of the thousands who perished in the attack that began with a jetliner flying over Pfeifer's head. Almost 10 years later, Obama was here to mark that justice had finally been done.He returned to Washington having given actual comfort to the families. He left the firefighters at Engine 54, Ladder 4 saying he was not just a "regular guy" but "one of the guys. "They do not doubt he will keep after Al Qaeda as long as there is a threat. The SEALs and the rest of our military are sure to be ready to do whatever is needed. And here in New York, the chief who saw the war start will keep doing his job."Al Qaeda is not just one person," Pfeifer said.