Lived in a rural suburb of Denver when my kids were smaller. (9-14y.o.) The coyotes were VERY thick in the area and equally aggressive. It got to the point where nightly we would hear the yipping that they used to communicate while they were running down prey, then silence when they caught it. The kids started coming home in the evening saying as the sun started to go down the coyotes would start to follow them. The thing that prompted some changes was when they came in, and ran in the door terrified saying a pack had followed them making those sounds. They were on their bikes at the time and able to get safely home, barely. I called the local LE and asked if they had heard anything along those lines. Turns out new building in the area had concentrated them near our house and they were killing pets and scaring joggers pretty much daily. Too close to town to shoot, too many to handle that way anyway. Bought the kids bear pepper spray, best I could do. Part of the reason we moved not too long after.