By John Blake, CNN

(CNN) - David O'Brien couldn't help himself. After the September 11 terrorist attacks, he became obsessed.

O'Brien read the stories of 9/11 victims over and over, stunned by what he was discovering.

He read about the firefighters who marched up the smoke-choked stairwells of the World Trade Center, though many knew they could die; the beloved priest killed while giving last rites as the twin towers collapsed; the passengers on hijacked planes who called their families one last time to say, "I love you."

"I was obsessed with these stories," says O'Brien, a Catholic historian at the University of Dayton in Ohio. "There were so many stories of self-sacrifice, not just by the first responders, but by people fleeing the building. There was this revelation of goodness."

O'Brien saw an Easter message in 9/11 - good rising out of the ashes of evil. Yet there were other religious messages sent that day, and afterward, that are more troubling, religious leaders and scholars say.

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