Teenager helps pregnant attack victim.(Adam Silvis )

Seventeen-year-old Adam Silvis was riding an ATV through a wooded area of Wayne Township, Pennsylvania, when he saw a woman's seemingly lifeless legs sticking out of some brush and another woman trying to cover the body. Sizing up the situation, he knew that something was radically wrong, but opted to feign disinterest before reacting.

"I'm by myself here. I didn't have a cell phone. I didn't know what I'm getting myself into. I just acted as calm as I could," Adam told the Pittsburgh Post-Gazette. "I acted like I couldn't see what was going on but it was obvious," he said in an interview with ABC News.

After memorizing the license plate of the woman's vehicle, Silvis sped home to tell his tether about his discovery. The elder Silvis grabbed his gun, mounted a second ATV, and followed his son back to the scene. When Mr. Silvis asked the woman, later identified as Peggy Jo Conner, what had happened, she evasively replied, "nothing." Silvis told his son to go back home and have his mother dial 911 to report the crime to the state police.

The story that developed was bizarre. The woman lying on the ground was Valerie Oskin, a 30-year-old woman who was eight months' pregnant. Peggy Jo ...