Guardian: "1,624 mass shootings in 1,870 days"

Wikipedia (sourced from CNN): "90 mass shootings between 1966 and 2012"

They both use the same definition of mass shooting (four or more victims) so how is there an order of magnitude difference between their numbers? Ah, I see. CNN excluded gang violence in their numbers, and the Guardian included it. Seems like they may have a few biases of their own.

I don't want to sound picky, but wikipedia isn't the best source on controversial topics.