How American Sniper made it to the big screen

NEW YORK -- With a blockbuster opening weekend, American Sniper has shattered box office records.

But not everyone is praising this real-life story. Michael Moore tweeted this week: "We were taught snipers were cowards. Will shoot you in the back. Snipers aren't heroes."

He later clarified the statement, saying people have a right to defend themselves, but the comment is sparking debate online.

And it is being echoed on a billboard in Los Angeles, spray painted with the word, "Murder".

But despite the controversy, the movie is still a critical success, earning six Oscar nods. And the film's lead, Bradley Cooper, says this was one of the toughest characters he has played.

Chris Kyle became one of the most famous sharpshooters in American history and one of the best.

Bradley Cooper gives one of his best performances as a man caught between his duty to his country and to his family.

"You get a sense of what it's like to deal with those two worlds, you know for a soldier and their family to deal with this almost schizophrenic nature of that lifestyle," said Cooper.

British actress Siena Miller is almost unrecognizable as Kyle's wife. "You can hear by the way I talk that there were lots of differences, but at the same time there was a lot I could relate to within Taya & her spirit."

"Taya" Kyle provided Cooper with hundreds of private, even intimate emails between the couple so both performers could play people quite unlike themselves.

"I'm about 185 pounds from Philadelphia and he was 230 from Odessa, Texas, and I'm not in the military. He was a Navy Seal on 4 tours you know I never shot a sniper rifle," he said.

The star learned how to handle weapons and spent many hours each day in the gym to bulk up, then used all that to tap into the spirit of the man who was murdered after he came home from war.

"I felt protected by him quite honestly because it was such a huge, bold task that I was petrified of honestly whether I could even do it so once I got the size and the voice, he kind of took care of the rest of it," Cooper said.

"American Sniper" gave director Clint Eastwood the best opening of his long career when his movie went into theaters everywhere last Friday. It has earned high marks from veterans who served in Iraq.

But perhaps the highest compliment came from Kyle's real life wife.

"His wife felt she'd spent time with her husband and that's all the validation you need."