David Oyelowo on chilling new movie, "Captive"

David Oyelowo, who was acclaimed for his portrayal of Dr. Martin Luther King, Jr., in the movie, "Selma," is back on the big screen. But this time, he takes on a very different role.

The actor joined "CBS This Morning" to discuss his latest, true-to-life thriller, "Captive," in which he plays Brian Nichols, who was at the center of a huge manhunt in the Atlanta area 10 years ago after killing four people while escaping from a courthouse.

The story focuses on the relationship between Nichols and Ashley Smith, a woman he held hostage for seven hours, but ultimately inspires him to turn himself in.

Oyelowo shared some challenges of playing a killer on screen, describing it as not the "most comfortable."

"It all involves getting as deep into the head of the person as possible and someone who did what he did. ... There are dark spaces you have to go," he said.

But the actor said he was inspired to jump in by Ashley Smith, who--despite her husband's death from a drug-related incident, her own struggle with drug addiction, and losing custody of her daughter-- he says went on to live "beyond" the event.

Oyelowo says Smith, who was also on set for a lot of the shoots, was also very helpful because he couldn't get in contact with the real-life Brian Nichols, who is currently serving multiple life sentences.

"Something about her made his humanity kind of resurface and that's why I believe she didn't become his fifth victim," Oyelowo said. "Thinking about his son ... also Rick Warren's book, 'The Purpose Driven Life,' that they read with each other -- it was a human exchange."

The actor is also nominated for an Emmy for his performance in the HBO movie, "Nightingale," in which he plays a man suffering from an identity disorder. In order to fully immerse himself in the character, he even moved out of his home in order to distance himself from his family while shooting the film.

"I think telling the truth costs as an actor," he said. "Yeah you go in hard."

But going back to his latest role, he added, "Brian Nichols--that left me feeling pretty hollowed out after playing that role."

"Captive" opens in theaters Friday, Sept.17.