How many people have to die before a shooting is considered a “mass shooting”?
There is no legal definition. Congress defines a “mass killing” as 3 or more killings in a single incident. Other sources say at least four must be injured, but not necessarily killed.
The website, massshootingtracker.org, has their own take on the definition. They define as mass shooting to be “an incident of violence in which 4 or more people are shot”.
The site is an unfunded, crowd-sourced effort featured in the Washington Post, The New York Times, CNN and MSNBC. They track every mass shooting (by their definition) since 2013.
Take a look at the information. According to their data, so far in 2017 there have been over 530 deaths as a result of mass shootings. By the end of October 2016 the site had 521 deaths reported.
Since the beginning of 2013 the site reports 1,890 mass shootings. 378 of those have been in 2017.
See the date for yourself here.