The first thing to know is how the human body reacts to relentless stress. Men tend to regress to a more child-like state. As with an illness, the smallest nuisance can make them angry, whiny, complaining, and self-centered. They can behave like a sleepy child. It's not their fault; it's one of the body's warning systems saying "Hey! I need a break!"
In the face of emotional pain, fear or stress, humans tend to turn down their sensitivity dials to numb, reaching the point of functional coma. This means that your officer won't want to have any important conversations or emotional discussions, and one-syllable words may become his vocabulary. This is a warning sign. I imagine this was programed as a survival perk in the Stone Age, allowing our emotional self to take a back seat so the logical self can drive and make decisions the emotional self could not. In this century, it's more of a hindrance. Sleep patterns change; eating habits go wild; and video games or movies may become an escape. If these activities become all they want to do, it's a warning sign.
You may begin to see your previously social drinker having a drink every night, maybe two or three. Maybe he goes to the bar down the street every night after shift. Maladaptive coping skills tend to run rampant in the policing world for several reasons. Cops are tough and don't talk about their feelings. Cops like cops, so they hang around cops who are tough and don't talk about their feelings. Unless their spouse is also a cop or dispatcher, they're not in this group, which further pushes them away. With the other previously listed behaviors, it's no wonder the divorce rate in law enforcement has reached 80 percent.
His job may be to protect the community, but our job is to protect him, our children, and ourselves. I would never advocate staying in an abusive marriage. Short of that, a little understanding goes a long way. Knowing what he's going through is half the battle. His outbursts and any immature behavior or otherwise maladaptive coping mechanisms are not your fault. Say it with me, not my fault. Very good.
The most important thing to remember is, don't respond with anger because that only escalates the situation. A calm and soothing voice does wonders for anger and other outbursts. I call it my 911 voice. "I can help you," I will say. "Tell me what the problem is, and we will work together to solve it." This works much better than calling him any name you could muster.