[cnn-photo-caption image=http://i2.cdn.turner.com/cnn/2009/images/06/02/art.tiller.kake.jpg caption="Dr. George Tiller was one of the few U.S. physicians who performed late-term abortions."] From CNN's Carol Costello and Bob Ruff Killing doctors who perform legal abortions is rare in this country—but it happened again over the weekend. Dr. George Tiller, who performed late-term abortions at his Wichita, Kansas clinic, was shot and … Continue reading Who's responsible for Tiller's killing?