"Russell had been deployed to Iraq three times and was just weeks from returning home, officials said. He's also served in Bosnia and Kosovo." Sgt. John Russel had combat stress. The nut at Ft. Hood did not. He was a Muslim that was against the war and took it out on innocent people. He was a domestic terrorist in the 1st degree.
Most muslims are not really nuts, but Islam with its primitive nature breeds a much higher level of violence than most other religions. There is a substantial number of Imams that preach hate and violence and it leads to a following of people willing to do it. 1 Billions muslims, 5% radical = 50 million jihadists, suicide bombers, etc.