OWOSSO, Mich. — A man carrying grudges against several people in town set off on a shooting spree Friday morning, authorities said, killing an abortion protester outside a school because he didn't like that the activist carried a sign with graphic images of a fetus in front of students.

Before he was done, the gunman drove to a gravel pit and shot and killed the owner, apparently for different reasons, police said. Authorities believe they stopped a third killing by catching up with him before he could pull the trigger...