Authorities say recent attacks in Philadelphia and Chattanooga, Tennessee, may have involved multiple shooters.
According to the Gun Violence Archive, the first weekend of June saw at least 12 people killed and 38 injured in mass shootings — defined as incidents where four or more people are shot or killed, excluding the gunman.
That marks an increase from the Memorial Day weekend, when nine people were killed and more than 60 were injured in similar attacks.
