NEW YORK—A smiling group of tourists, some giving the thumbs-up sign or making "bunny ears" behind one another's heads, posed to have their pictures taken Tuesday outside the Dakota apartments, on the very spot where John Lennon's blood splashed against the building and pooled on the sidewalk as he died. "Smile!" said the photographer to the happily married couple and their three children as he stood where Mark David Chapman gunned down Lennon on Dec. 8, 1980, causing a shrieking Yoko Ono to cradle her husband's bullet-riddled body. "There! Perfect. Want to do a fun one where all of you do something silly?" The group then hailed a taxi to drive them downtown so they could have their smiling photo taken on the same spot where Islamic extremists killed thousands of Americans on Sept. 11, 2001.