The New York Times has details about the attack:

"The American military command in Baghdad said the CBS journalists killed in Baghdad were embedded with a unit of the 4th Infantry Division when they were hit by a car bomb at about 10.30 a.m. local time. A CBS spokesman said the journalists were outside the armored Humvee in which they had been traveling, wearing body armor, when the explosion occurred near Tahiriyat Square in east Baghdad.

That is about a mile east of the American headquarters complex situated across the other side of the Tigris river in the heavily fortified Green Zone.

The statement by the United States command said the four who died were victims of 'a vehicle-borne improvised explosive device,' or a car bomb.

Iraqi employees of The New York Times who visited the scene after the attack said the bomb exploded on a street just south of an intersection known as Basil Building Square, opposite a compound with two schools. They said the blast had left a crater in the road and a carpet of broken glass as it shattered windows in homes and shops as much as 100 yards from the explosion.

Television footage taken by an Iraqi camera crew shortly after the bombing showed what appeared to be a burning armored vehicle strewn sideways beside the median strip, with an Iraqi fire engine hosing down the wreck. The site of the attack is a few hundred yards west of Tahiriyat Square."