Nicholas Carlson
After his ex printed out the invite and delivered it to the local police station, the police arrived at Gagnon's home and arrested him.
Gagnon's attorney argued that he shouldn't have been arrested because the Google+ notification was sent automatically without Gagnon's knowledge.
Generally, when you create a Google+ profile, the site suggests profiles of people based off the contacts found on your Gmail. If a person in your Gmail contacts joins the network, the service will ask if you want to add that person to your "Circle" of friends.
It's possible that Gagnon's ex got that kind of notification from him after he joined the network.