I had a modicum of sympathy before reading the article. After all, he seems like a decent, well-intentioned man, even if he is wrong on the issue. He was volunteering to help mentor kids in a school sponsored program.
But let's see... he was charged with two counts of felony possession of a firearm on school grounds. It's not like he made two trip to the school, so I'm guessing he had two guns. He likely had a gun on his belt and another backup gun somewhere on him. How on God's green earth do you not realize you have one, let alone two, guns on your person?
Then, despite being in phone contact with a police lieutenant during the event, he never tells the cops he is armed (apparently the lock down didn't jog his memory). They only discovered that he was armed when they pat down each person as they cleared the school. It sounds like he was hoping to get away with it.