"The US has reported at least 45 mass shootings in the last...

"The US has reported at least 45 mass shootings in the last month"

"The US has seen at least 147 mass shootings in 2021, according to data from the GVA, a non-profit based in Washington."

https://edition.cnn.com/2021/04/16/us/mass-shootings-45-one-month/index.html

Numbers may be under reported as the CNN data source

"considers an incident to be a mass shooting if four or more people are shot, wounded, or killed, excluding the gunman".