bedrock-samples/resource_pack/animation_controllers/wither_skeleton.animation_controllers.json

{
	"format_version" : "1.10.0",
	"animation_controllers" : {
		"controller.animation.wither_skeleton.attack" : {
			"initial_state" : "default",
			"states" : {
				"chase_target" : {
					"animations" : [ "wither_skeleton_attack" ],
					"transitions" : [
						{
							"default" : "!variable.has_target"
						}
					]
				},
				"default" : {
					"transitions" : [
						{
							"chase_target" : "variable.has_target"
						}
					]
				}
			}
		}
	}
}