Graham told Napolitano that the Secret Service officers and supervisors involved should have known their conduct was wrong: "I don't think it's a lack of training."
The White House said Wednesday that the conduct of the employees punished in the ongoing scandal was "inappropriate" and unacceptable for people representing the United States abroad.
"The president said that if the accusations that had surfaced at the time turned out to be true, he would be angry. And of course, he is angry," presidential spokesman Jay Carney told reporters traveling with Obama on Air Force One.
The Judiciary Committee hearing was the first time Napolitano has faced public questioning from lawmakers since the scandal. Senators praised the speed of the probe and the affinity that Secret Service Director Mark Sullivan had for answering senators' questions before they are asked.
Napolitano said the Homeland Security Department's inspector general is also supervising the investigation and using "the investigatory resources of the Secret Service." She added add that she expected the inspector general to do a complete investigation.
Elsewhere on Capitol Hill Wednesday, House Speaker John Boehner said the scandal is an embarrassment to the agency and the United States, but stopped short of calling for an independent investigation.
"What I'm looking for are the facts. I don't want to just jump out there and make noise just to be making noise," Boehner told reporters. "Let's get to the bottom of this."
Associated Press writers Robert Burns, Julie Pace, Ben Feller, Jim Kuhnhenn and Donna Cassata in Washington and Lolita C. Baldor in Brasilia, Brazil, contributed to this report.
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