ISLAMABAD %E2%80%93 Osama bin Laden was holed up in a two-story house 100 yards from a Pakistani military academy when four helicopters carrying U.S. anti-terror forces swooped in the early morning hours of Monday and killed him.

Flames rose Monday from the building that was the apparent target of the raid as it was confirmed that the world's most wanted fugitive died not in a cave, but in a town best known as a garrison for the Pakistani military. A U.S. official said one of bin Laden's sons was also killed in the raid along with three others, but the official did not name the son or the others killed.

Pakistani officials and a witness said bin Laden's guards opened fire from the roof of the building, and one of the choppers crashed. The sound of at least two explosions rocked the small northwestern town of Abbottabad where the al-Qaida chief made his last stand. The U.S. said no Americans were harmed in the raid.

Abbottabad is home to at least one regiment of the Pakistani army, is dotted with military buildings and home to thousands of army personnel. Surrounded by hills and with mountains in the distance, it is less than half a days drive from the border region with Afghanistan, where most intelligence assessments believed bin Laden was holed up.

The news he was killed in an army town in Pakistan will raise more pointed questions of how he managed to evade capture and whether Pakistan's military and intelligence leadership knew of his whereabouts and sheltered him. Critics have long accused elements of Pakistan's security establishment of protecting bin Laden, though Islamabad has always denied this.

Abbotabad resident Mohammad Haroon Rasheed said the raid happened about 1:15 a.m. local time.

"I heard a thundering sound, followed by heavy firing. Then firing suddenly stopped. Then more thundering, then a big blast," he said. "In the morning when we went out to see what happened, some helicopter wreckage was lying in an open field."

He said the house was 100 meters (yards) away from the gate of the academy.

A Pakistani official in the town said fighters on the roof opened fire on the choppers as they came close to the building with rocket propelled grenades. Another official said four helicopters took off from the Ghazi air base in northwest Pakistan.

Last summer, the U.S. army was based in Ghazi to help out in the aftermath of the floods.

Women and children were taken into custody during the raid, he said.

Both officials spoke on condition of anonymity because of the sensitivity of the information.