Leroy Carhart was at his abortion clinic near Omaha when he got the phone call. It was Sunday morning, a little after 10, and the doctor was in surgery. He felt his cell phone vibrate. Carhart ignored it, finishing the abortion before checking his phone. The number for George Tiller's head nurse in Wichita, Kans., flashed on the screen. The timing was unusual; Carhart didn't often hear from Tiller on Sunday mornings. He thought it might have to do with a patient, maybe an emergency. But when Carhart called back, Tiller's nurse was crying. "George is dead," she told him through sobs, relaying the news that Tiller, the late-term-abortion provider, had been fatally shot at his Lutheran church.
Carhart was scheduled to work in Tiller's clinic the next day; he was one of three abortion doctors who took turns assisting there. His car was already packed for the five-hour drive from Omaha to Wichita he'd...