NEW : Lawyer : Testimony about the killings of dozens of teenagers `` will be toughest day '' for prosecutors. He considers bombing that killed eight a failure because the targeted building did not fall . He admits killing 77 people in a gun-and-bomb rampage , calling it `` necessary ''
NEW : Lawyer : Testimony about the killings of dozens of teenagers `` will be toughest day '' Anders Behring Breivik says he also wanted to decapitate an ex-prime minister . He considers bombing that killed eight a failure because the targeted building did not fall . He admits killing 77 people in a gun-and-bomb rampage , calling it `` necessary ''