Though authorities have not offered a definitive account of Dear’s motive, he mentioned “no more baby parts” to law-enforcement officials after his surrender, and at least one acquaintance said he praised people who attacked abortion providers as doing “God’s work,” according to the The New York Times.

Attacks meant to intimidate abortion providers and clinics have become a tragically common element of the American abortion battle. The first abortion provider to be murdered was David Gunn, in 1993, and perhaps the most infamous recent slaying was that of George Tiller, who was shot in the head as he served as an usher at his church in 2009. Overall, anti-abortion violence has killed 11 people, and that’s not counting dozens more bombings, attempted murders, and even acid attacks tracked by the National Abortion Federation.

Abortion Clinic Violence Incidents by Year (1976-2005)

There’s been an uptick in threats against reproductive health-care facilities since this summer, when the Center for Medical Progress, a pro-life organization, began releasing videos showing Planned Parenthood officials discussing fetal tissue.

“It is likely criminal or suspicious incidents will continue to be directed against reproductive health-care providers, their staff, and facilities,” an FBI Intelligence Assessment warned in September, according to CBS News. Last week, that nightmare came true.

Anti-abortion terrorism, like all terrorism, spreads fear among far more people than it kills. (This is, alas, the point of terrorism.) Very few people will actually be gunned down on a Tunisian beach, but tourism there is plummeting anyway. Similarly, for people who attack abortion clinics, sowing fear is part of the plan.

But does it work? Attacks on abortion clinics are ghastly and take a harsh toll on the communities where they occur—but do they actually discourage abortion?

Anti-abortion violence actually peaked in the 1990s, and that era also saw a decline in both abortions and abortion providers. In 1993, the year before President Clinton signed a law prohibiting anyone from forcibly obstructing abortion clinics, 50 percent of clinics reported being the targets of violence and harassment.

When the economists Mireille Jacobson and Heather Royer examined whether these attacks were actually reducing the demand for or supply of abortions, they found that the effect was modest. In targeted areas, an attack on a clinic typically reduced the number of providers in the area by 6 to 9 percent, and the number of abortions by 8 to 9 percent. (The impact was felt more severely outside of hospitals: Clinic-based abortions and providers dropped by 10 to 14 percent.) When a murder happened, the effect was even more pronounced. Both abortions and providers decreased ten-fold, and they stayed at that level for years.