“The House passed two bills Thursday to require background checks on all firearms sales and transfers and to allow an expanded 10-day review for gun purchases.” (AP News)
Read the bills here and here. (Congress.gov)
As you’ll see, each side cites different examples to validate their claims. This 2020 article from the Los Angeles Times gives a breakdown of how different gun laws might have affected the 167 mass shootings that have occurred in the US since 1966 had they been in place, and this 2019 article from AP News...