Is there a sociological explanation of mass shootings ?

Yes. Intelligent people who are shunned and bullied and told they will never amount to anything  [apparently a dude called Jesus said: if you tell your neighbour he is nothing, in your heart you have already killed him] can take revenge by killing those who did the bullying and the shunning

and then take their own

There probably isn't a one size fits all explanation for mass shootings.  One of the shooters in Columbine came across as being a nihilist, who stated that people would be better off if the never existed.