Justin Chambers, who plays a protective father and police detective on the trail of the real-life 1960s Zodiac serial killer in the film The Zodiac, which opens Friday, can relate very personally to his character.

The life of Grey's Anatomy star and Springfield, Ohio, native was turned upside down during his freshman year in high school. His parents, John and Pam, both sheriff's deputies, were assigned to two heinous murders on the outskirts of town.

Chambers, 35, then tells USA Today about a mischievous childhood friend of his named Rodney. A neighborhood man thought Rodney and some other kids were stealing from him. Then he lost it.

"One day, the old guy just flipped out and went to my friend's home and shot my friend, his baby brother and their other siblings," Chambers said. "Then later that summer, there was another incident where a woman and her son were butchered by her boyfriend. That's as evil as it gets."

These incidents from his youth affected Chambers deeply as he prepared for The Zodiac. He confides that the film's twisted subject matter forced him to confront his faith in God, but that he emerged with renewed belief in both good and evil.

"I went through a rough spiritual awakening doing this film, asking myself, 'Why does evil happen?'" he said. "Evil lurks everywhere," he concludes. "I've met people who have some serious, pathological issues with no conscience. I think God gives everyone a meter, and it's up to you to choose right or wrong."

At 18, Chambers left Springfield for Paris, where he worked as a fashion model. But his life bore little resemblance to that of his "emotionally retarded" Grey's Anatomy playboy character, Alex Karev. He's been off the market since he was 22 and met his wife, Keisha, a former booker for a modeling agency. Chambers' 12-year marriage is the polar opposite of Alex's on-again, off-again relationship with Izzie. He and Keisha have five children: Isabella, 11, twins Maya and Kaila, 8, Eva, 6, and Jackson, 4.

"I've been a parent most of my adult life, so I don't know any other way," says Chambers, who recently moved from New York to Los Angeles, and has coached his twin girls' soccer team in the past. "But five is enough."

Now that Grey's Anatomy is a hit, the whole family will finally will join him in Los Angeles this summer.

"I came out here and didn't know it would be such a success. When it's over, I'm out! Back in New York, which will always be my home," Chambers said.

To read more of Justin's thoughts on The Zodiac, check out another recent interview of his. Interestingly, another film about the same case, called Zodiac, directed by David Fincher and starring Jake Gyllenhaal, Gary Oldman and Robert Downey Jr., will be released later this year.

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.