Unanswered: movie like stand by me/lord of the flies

ı saw a guy on turkish forum he is trying to find this movie. Its not the lord of the flies. Movie is about a man and his daughter goes cemetery and he tells his childhood memory about finding lost kid dead body in cave. Man and friends stays in forest sometimes and they fight with another group of kids. Group of kids attacking with smoke grenades. sometimes they are passing through lake and sometimes military areas.At one scene they are passing military area and girl steps on grenade and other kid kicks grenade to save her. end of the movie they find the kid body in cave and it has a locket with bird sign (eagle or pigeon).Kid finds in cave haves a kid gang in the past but his friends left town and he stayed alone in this cave this is the movie and no one can find in turkish forum. maybe ı make some translate problems sorry about it. İts not my native language.