Atlanta police described the incident as a "domestic situation" involving a man who shot a woman after a row, the Associated Press news agency reports.
The armed man was shot by a CNN security guard, police said.
The CNN.com office was briefly evacuated but no-one within the newsroom was hurt. Parts of the complex remain closed as officers investigate.
Witnesses reported seeing a woman being shot in the face following an argument by escalators near the main entrance to the complex.
Police spokesman James Polite said the woman had been treated by paramedics but had died on arrival at Grady Hospital.
'Big boom'
Laura Bernardini, a producer for the CNN television network, described how she had gone for lunch in the complex when she heard screaming and saw people running for cover.
"People were saying 'we've heard gun shots, we've heard gun shots'," she said.
As well as the CNN newsroom, the complex includes the Omni Hotel, a large atrium and a food court, and is connected to Philips Arena, home of the National Basketball Association's Atlanta Hawks.
Atlanta resident Trina Johnson, 44, told AP she was in the food court with her family at the time of the incident.
She said: "All of a sudden we heard a big boom. We thought it was an explosion. We didn't see the gun. Everybody just started running."
A domestic dispute resulted in shots being fired around the Headquarters of CNN in Atlanta, GA on Tuesday, killing a woman and critically wounding the ex-boyfriend who pulled a gun on her according to the authorities. The man and woman were arguing near the main entrance of the complex when the man shot her, police officer James Polite said. The armed man was then shot by a CNN security guard.
CNN Headquarters, Atlanta
The woman was Clara Riddles, 22, of College Park, said Caryn Kboudi, a spokeswoman for the Texas-based Omni Hotel chain.

Upon arrival at Grady Hospital, Riddles was pronounced dead said hospital spokeswoman Denise Simpson. The shooter, a man in his late thirties, and Riddles's ex-boyfriend, Arthur Mann was in stable condition. He is being charged with murder, Police said.

Victims were seen being carried out of the building on stretchers. Mann's face was covered in blood and his shirt had been removed.

CNN also reported that the offices of its Internet operations, CNN.com, were immediately evacuated. Video footage also showed police pointing guns at a man lying on the ground at the bottom of an escalator inside the building.

An announcement over the building's PA system announced that there had been gunfire "with potential casualties." Police cordoned off an area by the escalators near the main entrance, facing Centennial Olympic Park - a park that had been the site of a bombing that killed a woman and injured more than 100 people during the 1996
Summer Olympics.

"I heard four or five shots. I really didn't see it. I got out of there quick," said Jas Stanford, 27, who had been helping take down a temporary stage in the park used for college basketball's. When Mann fired his gun, security guard Odell Adams shot him, said Lisa Tobias, director of corporate responsibility for Turner Broadcasting System, which operates CNN.

Turner officials are satisfied with the response of Adams and the Atlanta police, Tobias said. The company does not discuss its security publicly, she said, but "we are constantly evaluating our procedures to make sure that we have ensured the safety of CNN employees and visitors." Besides the Omni Hotel, the CNN complex also includes a large atrium and a food court. It is connected to Philips Arena, the home of the NBA's Atlanta Hawks.

In the food court, Trina Johnson, 44, of Atlanta, was with her daughter on a family outing. "All of a sudden we heard a big boom. We thought it was an explosion," Johnson said. "We didn't see the gun. Everybody just started running."

Soon afterward, CNN coverage of the shooting was being shown on large-screen televisions inside the atrium, near where the shooting had taken place.

On Monday, a woman was shot and killed at the University of Washington in Seattle by an ex-boyfriend on whom she had sought a restraining order, police said. The man killed himself afterward.