Law Center

ALEXANDRIA, Virginia (CNN) -- Jurors saw gripping videotape of jetliners crashing into the World Trade Center and people jumping to their deaths as the nation's first trial about the September 11, 2001, attacks resumed Thursday.

Former New York Mayor Rudy Giuliani described the horrific scene as the prosecution's first witness in the final phase of al Qaeda conspirator Zacarias Moussaoui's death penalty trial.

"I was watching this man throwing himself out, fleeing the flame and the smoke," Giuliani said. He said he saw the man hit the pavement. (Watch 'extravaganza of grief' -- 2:45)

"It switched my thinking about this," Giuliani said.

He testified he later saw what he called the most indelible 9/11 image seared into his memory -- a couple holding hands as they leaped from one of the flaming towers.

"We are in uncharted territory. This is much worse than anything we have ever faced before," Giuliani said he told his police commissioner.

The government called Giuliani to summarize the impact of the terrorist attacks.

Giuliani's testimony followed brief opening statements by both sides to start the trial's second half.

When he was told the first plane had struck the north tower at 8:46 a.m., Giuliani said he immediately left a breakfast meeting in Midtown Manhattan.

As he arrived on the scene in Lower Manhattan, he said he saw a second jetliner crash into the south tower.

Giuliani: 'This was war'

"By the time the second plane hit, we knew it was a terrorist attack," Giuliani said. "This was war. This was a battle."

Jurors