It sounds like they're saying it was not a shooter shooting at the crowd per se, but a member or a number of members of the crowd engaging in shooting.
You're mixing your metaphors. While school shootings are an American tradition, pedophilia is ubiquotus worldwide and not at all unique to the USA.
The United States has a long history of university shootings. Virginia Tech comes to mind immediately, not to mention Michigan State just last year.
True to form, even the cops get involved sometimes. For example Kent State or South Carolina State College. Those are a bit old now, but I'd say there are some more recent examples.
I’m pretty sure he’s making a joke about how we’ve been seeing more elementary aged school shootings and how it’s so common now that having it at a university is “unusual”.