Very very saddening..Allahu Musta'an. Yes the perpetrator might have been a victim of mental illness however he could have also been motivated by brainwashing, racist hatred, etc. There is no way anyone can justify the crime as anything short of cold blooded murder, and if this criminal is not prosecuted to the toughest degree then lest assured crimes of this nature will continue,Audubillah! And yes sadly it is people like him that bring disgrace and disrepute to all those well intentioned brave soldiers the world over!