This might be affected in 1.10.1, but I'm not sure. I summoned a skeletal horse with the command,

/summon EntityHorse ~ ~ ~3 {SaddleItem:{id:saddle},ArmorItem:{id:diamond_horse_armor},SkeletonTrap:1b,Tame:1b}

. The horse summoned is invisible but can still be ridden(the shadow is still visible). The saddle and horse armor are on the horse, however; they both have a damage value of 0. While riding the horse I typed the command "/kill @e[type=EntityHorse]" to kill all the horses. This didn't work out though, the screen went black and the f3+t degub shortcut did not work. I quit the minecraft application and restarted the game, logging back into the world and, the horses were gone. I summoned the horse again and WITHOUT riding it I did the same command, "/kill @e[type=EntityHorse]" and the same thing happens, a black screen. I was able to spawn and kill the horses before I rode one while doing the kill command.