Very sad news A police horse is still just a horse, unfortunately. I used to work with police horses in a care and training capacity (not police officer) and I can tell you now - they aren't all quiet. Some are very far from quiet.
But what the regular patrol horses (and especially public order/riot qualified horses) are is very well acclimatised to the job of walking down the street with trucks and cars inches away, sidepassing no questions asked, not reacting to frightening noises, standing when told, etc etc.
The core of the training for a police horse lies in the fact that they MUST be able to be ridden mostly through leg and seat (anyone can pull on the reins in public!), and they MUST always react to the riders requests, immediately. They may not have the finesse of a pure dressage elementary/2nd level horse, but they need to have those basics solidly trained into them to be safe. No ifs, no buts, no excuses.
The unit I worked in had a longer term system than many others, but it made for very reliable patrol horses as they gradually passed all the requirements. Breaking in; basic flatwork establishing forwardness and obedience; many outings to various low pressure surroundings; gradually introducing more intense pattern work, laterals etc; starting city street rides in groups; commencing "real" patrols in pairs slowly increasing in pressure of situations, and eventually habituating them to the full-on riot training.
Some of the police horses I've worked with have been anything but quiet. Often they are naughtier "at home" in the arena, through boredom, playfulness or whatever, but settle down to do their job when out on the street. One in particular was a highly nervous, "hot" horse ridden only by the more experienced riders. Very touchy, difficult and couldn't be ridden with lots of hand - a definite seat/leg horse. Even on patrol he looks like he's about to jump out of his skin and he is the same in his stable - BUT, he is a brilliant patrol horse, extremely reliable, and in a public order situation copes better than lots of the "quieter" natured horses. He may be hot but he is very predictable.
A police horse has to be willing, well trained and habituated to the scary things they have to face, and have the mental capacity to cope with the job. AND they often have to cope with a confusing number of riders while retaining their training!
A police rider has to be able to make those horses, and be their comfort and direction when things get tough. The police mounted units of the world do a tremendously difficult job, and it is a miracle there are so few tragic accidents like this considering what they face daily.
I feel terribly for the family and friends of the police officer who died, but at least they went doing something their loved ones can be proud of. It isn't always an easy job and I commend those who are brave enough to put their lives on the line patrolling the streets of the world on a creature with a mind of its own. Good on them
I work in Chicago and about 10 years ago, I complimented an officer on his very handsome, very fit but obviously aged partner. The officer beamed and told me that "Midnight" was 31. The horse looked magnificent. I would see them frequently and always detoured to their side of the street to say Hi and give Midnight a scritch.
One day, a little boy ran up behind Midnight holding a large paper fan. Before anyone could do anything, the boy swatted Midnight's hocks with the fan. My mind was spinning, already imagining a worst case scenario.
Midnight merely lifted his tail and pooped hugely, with utterly comedic timing. The officer, himself a comic, said (with equally impeccable timing) "See what you made him do?"
It wasn't too much longer that I ceased seeing handsome old Midnight and his officer. I'm sure that Midnight passed in a dignified manner. And I have no doubt that kid remembers his lesson.
Don't wrassle with a hog. You just get dirty, and the hog likes it.