Apparently there has been a string of arson's against pro-life pregnancy centers and a pro-choice group called "Janes Revenge" I am looking for links to more mainstream sources but the best mainstream source I could find was the hill. It's mostly been covered by right wing sources including Fox.
thehill.com
www.foxnews.com
buffalonews.com
Apparently this group has taken responsibility for several attacks.
en.wikipedia.org
Fortunately it does not seem that this group has yet graduated to killing people. Let's hope they don't.

New York police investigating suspected arson at pregnancy center
Credit: Getty Images The Amherst, N.Y. Police Department (APD) announced Tuesday that it is investigating a “suspicious” fire that occurred at CompassCare pregnancy center in Buffalo. “Twin City Am…


Oregon Pregnancy Resource Center fire considered 'suspicious in nature' by authorities
A Pregnancy Resource Center in Gresham, Oregon was heavily damaged during a fire on Friday, and federal authorities are considering the incident as "suspicious in nature."

Political violence blamed in arson at anti-abortion group's center in Amherst
Town police said a fire at CompassCare at 1230 Eggert Road, off Main Street, was reported at 2:30 a.m. Tuesday.
Apparently this group has taken responsibility for several attacks.
Jane's Revenge - Wikipedia

Fortunately it does not seem that this group has yet graduated to killing people. Let's hope they don't.