FIRST IMPRESSION: This is more of a snapshot, but I realize you did not set out to "set this up". Sometimes candids, such as this can work, and in this case it does.
CHALLENGE:This definately meets the challenge and in some ways exceeds it. He could have been talking on his police radio, but instead is using his cell phone.
COMPOSITION: The policeman seems to be at a little bit of and angle. This is a little disturbing to the eye as we tend to want thing straight. The top of the head in the corner is a bit distracting as well. Is it possible you could have cropped it out without losing the intent of the photo?
TECHNICAL: The shadows are a bit dark and distracting, but I realize that is because of time of day and the candid aspect of the photogrtaph.
You colors are nice and bright, you whites are dazzling without being blown out. Your DOF is appropriate for this image. Technically there are no glaring problems here.
CONCLUSION: A good interpretation of the challenge, well shot and executed. I gave this a 6 during voting.
Thanks for sharing and good luck in future challenges!