A conventional law enforcement approach of responding AFTER a cyclist is attacked does not work in a large park. What does work is using a pro-active approach. Send a tiny, young female officer up the trail alone. Have five or six large male officers a couple hundred yards behind her. Have other officers concealed in the woods up ahead. A dangerous assignment for the "bait", but the only sure way to catch the hoodlums in the act of an attack.
However, not many police departments are going to make protection of cyclists a top priority. So, cyclists need to ride in groups of at least three or four in high crime areas, and at least two of the four need to be large enough to inspire the "skinheads" to take a new direction in life.
One day, I was riding through a rough area and saw a gang of ten or fifteen teen-agers beating up a kid. I pulled up about fifty years away and called 911 on my cell. One by one, members of the gang saw me, and would elbow the guy next to him and take off running. I was mystified why they took off.
Later, I realized that my mountain bike was equipped much like the bikes of the bicycle police in the area (rear rack and lots of lights front and back), and my white helmet, blue shirt and blue shorts were somewhat similar to what those officers wear. I was tempted to make those clothes my standard "bad neighborhood" outfit.