Former New York City Mayor Rudolph Giuliani appealed for unity during his testimony before the National Committee Investigating the September 11, 2001 attacks. Mr. Giuliani encountered angry outbursts from some of the families of victims who died in the collapse of the World Trade Center towers.

Mr. Giuliani told Commission members that terrible mistakes were made on the day of the attacks, but he said the heroism of the day and the real enemy are what should be remembered. He added that the Commission should be focusing on ways to prevent further terrorist acts, not assigning blame.

In its first day of hearings Tuesday, some commission members and former city officials sparred over hard questioning about the chain of command on the day of the attacks and faulty radio communications equipment. Commission members praised Mr. Giuliani who became a national figure in the aftermath of the attacks for his leadership.

However, a number of victims' relatives interrupted the laudatory comments and Mr. Giuliani's testimony with angry shouts and insults. They say lives were lost because faulty communication equipment made it impossible to alert people inside the Twin Towers of the imminent collapse of the buildings.

Mr. Giuliani left the hearing room abruptly after his testimony. Outside, he told reporters the anger is understandable, but misdirected. ?I understood from the day this happened that people would react to it very differently,? he said. ?That is what you saw in that room. You have some family members very supportive of what the police and the fire [departments] did, very appreciative of the tremendous number of people that they rescued and then you have some people angry that they thought things went wrong, more people could have been saved. I attribute it to stress and the trauma that they are going through. You have to place your anger somewhere. I have always found that the place to place the anger is unequivocally at the terrorists.?

Commission members have also said that rivalry between the fire and police departments and confusion over command structures hampered rescue efforts.