No one knows. The vast majority of mass murderers are men, though there have been a few women who went on killing sprees.
Basically this is a very poorly understood type of crime. It's very rare, the perpretrators often don't survive, and the ones that do don't cooperate with investigators.
Since we don't know why anyone snaps like this, specualtion about why it's mostly men would be just that, specualtion.
I guess you never heard of Bloody Mary, Queen Of The Scots.
It's 2012. Women are capable too.
There were wayyy more girl fights at my school then guy fights.
Good Question
Hahah you really shouldnt have wrote this bro