Four SWAT (MP) were wounded during gunfire.
Or it's a gang and/or drug thing. That's going to be my guess.
FWIW, the big news in Colorado Springs is that there is a unit at Ft. Carson, several soldiers from which have arrested for a number of fairly motiveless murders -- a lot of bad apples in that group. I could see something like that being the case at Ft. Hood, too.