With that age gap you are asking for trouble - and your chick got it. He is attempting to flee because he knows what is going to happen. Outside time is great, but it needs to be done within the safety of an enclosure that protects the chick from actual physical contact with the older birds to prevent injury and trauma. If you are unable to protect the chick by direct supervision/presence while it is out, this can be accomplished with a very simple "playpen" of poultry netting, etc) or done when the older birds are confined to their own structure.