The sad part about this is all of the usual cliches have come out already.
-"he is such a quite reserve person, we can't understand why he would have done this"
-"he was a good officer and this is so out of character"
etc, etc, etc, blah, blah, blah
However if this story stays in the news more about his past will come to light and the exact opposite will prove to be true. The police would have been impressed with his "aggressive personality" and that will have also been the most obvious sign that he couldn't be trusted.