Two additional men are being sought after by the FBI for information on the murder of abortion provider Dr. Barnett Slepian.
FBI officials have not said why they are seeking Ronald Stauber and Michael Gingrich, but have called on police authorities across the country to search for the two men.
The October 23 murder of Dr. Slepian is believed to be linked to four other shooting attacks on abortion providers in Upstate New York and Canada.
James Charles Kopp, an anti-abortion activist with a lengthy arrest record, was previously named a material witness to the crime. Investigators believe Kopp has information about the murder and have been searching for him since November 4.