You can't have Communism in once country anyway, that's integral to Marxist thought and it's why nations like USSR, Cuba etc. have always called themselves Socialist, but a lot of Communists would even say you can't have Socialism in one country
Back on topic the gunman has said he acted alone -
http://www.bbc.co.uk/news/world-europe-14266815. He described his actions as "gruesome but necessary apparently"