It’s all hype by the media to boost their ratings. The active shooter possibility is so small it wouldn’t even be worth talking about if the media didn’t stir up such a (you-know-what) storm about it. Look at the breakout for 2017, the latest year exact numbers are available. Note that the mass shootings number for 2017 includes the Las Vegas concert incident so it’s higher than other years.
Source: CDC and Time
In comparison, how often do you hear about multiple fatality car crashes on the news? They rate one minute, once. Then they’re out of sight and out of mind. In 2017, the CDC figure for car fatalities is 40,231. Dead is dead, period. Run an internet search for “multiple fatality car crash” and limit the search period to the past month. The number you’ll find is shocking.