liam neeson natasha richardsonTheo Wargo/Getty Images for Lincoln Center

Liam Neeson may have become an unlikely action star, but underneath the tough exterior, the actor's sensitive heart still grieves for his late wife, Natasha Richardson.

Neeson confesses on "60 Minutes" that Richardson's death "was never real. It still kind of isn't." The actress, with whom he had two sons, tragically passed away in 2009 after suffering a head injury in a skiing accident.

"There's periods now in our New York residence when I hear the door opening - especially the first couple of years - anytime I hear that door opening, I still think I'm going to hear her," he says in the interview, which airs this Sunday.

Neeson also reveals that in her death, Richardson passed on the gift of life to three other people -- her heart, kidneys, and liver were donated. He believes she would've been pleased, and notes that they had made a pact to "pull the plug" should either one of them wind up in a vegetative state.

But even nearly five years later, Neeson still experiences bouts of tremendous sadness over the loss.

"It hits you. It's like a wave," he says. "You just get this profound feeling of instability ... the Earth isn't stable anymore, and then it passes and it becomes more infrequent, but I still get it sometimes."

Watch a clip from the heartbreaking interview below:

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