A new book on the 2012 presidential campaign claims that President Barack Obama told aides that he is "really good at killing people." According to Mark Halperin and John Heilemann, the authors of Double Down: Game Change 2012, Obama made the comment while discussing drone strikes last year. CNN's Peter Hamby noted the anecdote in his review of the book for the Washington Post.While the White House has not commented on the president's alleged remarks, senior Obama adviser Dan Pfeiffer on Sunday brushed off, but did not dispute, other reports from the book, including that campaign officials weighed replacing Vice President Joe Biden with former Secretary of State Hillary Clinton on the Democratic ticket. "The president is always frustrated about leaks," Pfeiffer said on ABC's "This Week." "I haven't talked to him about this book. I haven't read it. He hasn't read it. But he hates leaks." The quote comes in the context of both the drone program and the killing of Osama bin Laden by a special forces strike force. The passage also specifically references the death of another al Qaeda leader, Anwar al-Awlaki, who was killed by a CIA drone strike in Yemen on Sept. 30, 2011.