This kind of thing did not happen when I was in high school, and we had guns back then. This seems to be a snowflake generation epidemic.
Well it sure does happen now and doesn't really happen where people don't have guns so...
Actually, statistically speaking, the EU has more mass shootings at a more frequent rate with more casualties than we do.
Sources please.
Also mass shootings =/= school shootings.
Also you should consider that not all europe countries are involved in big anti terrorism stuff (which makes them a terrorism target), so some countries, e.g. denmark, norway, switzerland,... are quite safe, where as others like french are not as safe.
About the officer there: As far as I know, he thought that the shooter was outside (he said that in a phone call I think). So getting behind his car and wait for reinforcement was - from what I heared - what the protocol says to do in such a situation. I might be wrong here, also I'm not saying it was the right thing to do.