Those numbers are from 2009 through 2015. That's just cherry picking, because those years just happen to include Anders Breivik. I think its well established that the US is the market leader in mass shootings.
Edit: Also, the president of Crime Prevention Research Center is John Lott, who's a known gun rights advocate. Your source does not seem to be very impartial.
Edit: Also, the president of Crime Prevention Research Center is John Lott, who's a known gun rights advocate. Your source does not seem to be very impartial.