RIO DE JANEIRO — Stalking the halls of his one-time elementary school, 23-year-old Wellington Oliveira killed 10 girls and two boys, most with shots to their heads even as children begged him to stop, witnesses said.

Oliveira then took his own life after police gunfire struck his legs and sent him toppling down some stairs, but not before carrying out what crime experts are calling the worst school massacre in Brazil's history.

Witnesses said he entered the Tasso da Silveira school in Rio de Janeiro on Thursday armed with two pistols and an ammunition belt, shooting at students and repeatedly yelling: “I'm going to kill you all!”

“He had already killed a lot of children in the first floor and in the yard,” student Jade Ramos told the Globo television network. “He kept telling the kids to face the wall and was shooting at their heads. The children kept begging, ‘No, please!' There was a lot of blood, children agonizing on the stairs.”

Ramos said she escaped by running into a classroom, where a teacher locked the door and barricaded it with tables. Images taken with a cell phone and posted on YouTube showed students fleeing wildly, screaming for help, many with their white and blue school shirts soaked in blood.

SENDAI, Japan — Nearly a million homes suffered blackouts in Japan's northeast today after a new earthquake killed three people and piled more misery on a region buried under the rubble of last month's devastating tsunami.The northeastern coast was still reeling from the destruction wrought by a jumbo 9.0-magnitude earthquake on March 11, with tens of thousands of households without power or water. The 7.1-magnitude aftershock Thursday threw even more areas into disarray and sent communities that had made some gains back to square one.

BRUSSELS — NATO acknowledged today that its airstrikes had hit rebels using tanks to fight government forces in eastern Libya, but said it would not apologize for the deaths because no one told them the rebels had tanks.British Rear Adm. Russell Harding, the deputy commander of the NATO operation, said in the past, only forces loyal to Libyan strongman Moammar Gadhafi had used heavy armored vehicles.Harding says the military situation between Libya’s eastern coastal towns of Brega and Ajdabiya remains fluid, with the two sides engaged in a series of advances and retreats, making it difficult for pilots to distinguish between them.