I heard on the PBS News that El Paso and Dayton are the 250th and 251st mass shootings this year.
I found various numbers when searching the internet. This wiki article confirms there is no one accepted method of counting mass shootings:
"This is a list of mass shootings in the United States that have occurred in 2019. Mass shootings are incidents involving multiple victims of firearm-related violence. The precise inclusion criteria are disputed, and there is no broadly accepted definition.[2][3]
Gun Violence Archive, a nonprofit research group that tracks shootings and their characteristics in the United States, defines a mass shooting as an incident in which four or more people, excluding the perpetrators, are shot in one location at roughly the same time.[4] The Congressional Research Service narrows that definition further, only considering what it defines as "public mass shootings", and only considering victims as those who are killed, excluding any victims who survive.[2] The Washington Post and Mother Jones use similar definitions, with the latter acknowledging that their definition "is a conservative measure of the problem", as many rampages with fewer fatalities occur.[5][6] The crowdsourced Mass Shooting Tracker project defines a mass shooting as "an incident where four or more people are shot in a single shooting spree. This may include the gunman himself, or police shootings of civilians around the gunman."[7]
As of July 31, 2019, 248 mass shootings have occurred in 2019 that fit the inclusion criteria of this article. This averages out to 1.2 shootings per day. In these shootings, 979 people were injured and 246 died (for a total of 1,325 victims). "
List of Mass Shootings: