An updated article from the same source.

"Elizabeth Maine of Owosso said people would sometimes get upset with Pouillon and his graphic signs and would sometimes spit and scream at him.
"One man threw a piece of fruit at him and hit him in the head," said Maine.
Lori Lamerand, president and Chief Executive Officer of Planned Parenthood East Central Michigan, also expressed shock and sadness at the news.
"We want to be very clear that we have no idea if this was related to his views, but Planned Parenthood would never condone any sort of violence against anyone, regardless of their views," said Lamerand.
A suspect was taken into custody within an hour of the shooting. Lamerand said her office has not been contacted by police at this time and no link has been made to the organization.
"Certainly we do eveyrthing we can to ensure the safety and security of our clients, and if called upon, we would obviously cooperate with any investigation with the police," said Lamerand. "I am aware he's been a protestor at our offices in the past but I have had no personal contact with this man and did not know him personally."
http://www.mlive.com/news/flint/index.ssf/2009/09/owosso_antiabortion_activists.html