From the article linked to: "He was under active police surveillance at the time of the attack..."
@ Simon said, "There's going to come a time when people get tired of governments doing nothing to protect them and actively putting them at risk. There's going to come a time when people will protect themselves, proactively."
That is why where I live in the U.S. I legally carry concealed, and have for over forty years. I know there are always going to be those who will believe I am wrong and seek to disarm me and other law-abiding citizens who prefer not becoming helpless victims, but I would much rather carry a means of protection and never need it than to never carry and find myself or others in a situation where it was needed.