(Ed. note: This is a guest post by Kate Michelman, the former president of NARAL.)

They seem to have a preference, these extremists who murder in the name of religion, for killing when their prey is engaged in religious observance. Dr. Bart Slepian was shot to death after attending Friday night services at a synagogue. Now my friend Dr. George Tiller has been murdered at church -- not in a fit of rage, but in a coldly calculated crime. The moment I heard the news, my first reaction was, "Why wasn't he wearing his vest?" Dr. Tiller rarely walked out the front door of his home without draping his torso in kevlar. The killer knew enough to shoot him in the head.

George Tiller was among the most selfless of men I have ever known. Surely being stalked for a quarter-century or more by extremists who repeatedly called for his murder in public was not what this compassionate doctor had in mind when he started medical school. Nor was practicing medicine under armed guard, or having his clinic bombed, or being shot in the very arms he used to save lives. But Dr. Tiller did have one goal in mind when he embarked on his career: caring for his patients, which is precisely why he braved these threats. The intimidation of other physicians strengthened his resolve. It must also strengthen our resolve to protect the right he was murdered for upholding. The anti-choice movement is fond of casual yet inaccurate epithets like "abortion on demand." Dr. Tiller's murder is a stark reminder that women are still subject to indignities and dangers when exercising personal responsibility for their lives and those of their families. The work of our movement is far from finished, and there could be no more fitting tribute to Dr. George Tiller than renewing our commitment to it and ensuring that women who need services and those who provide them have safe and dignified access to them.

Just a couple of weeks before his death, I heard from Dr. Tiller, and the reason for his call said so much about him. He was the one being stalked and escorted by bodyguards, but he wanted to know how I was doing. Today, George Tiller, I'm doing poorly. Our world is doing poorly for having lost you. But your courage will inspire us to draw on our own strength and carry out the work for which you gave your life.