Hate to on this Sunday feature killings, but the USA had another  mass shooting yesterday , in Birmingham, Alabama.   Four were killed and more than 20 injured.   Authorities are not sure who or how many were responsible.   No suspects yet.  You can be pardoned for not even knowing this happened, for something similar occurs all the time. There have been more than 400 mass shootings in the U.S. this year. The  FBI defines mass shooting  as an event in which one or more individuals are actively engaged in killing or attempting kill people in a populated area.  Implicit is the use of firearm.  Usually needs to have at last three deaths. ONE THIRD of all the world's public mass shootings between 1966 and 2012 occurred in the U.S.  Size of circle indicates relative number of shootings. Not sure why that period ended more than twelve years ago, but that was from  Wikipedia , and until 2012 there have been 4,011 mass shooti...