looks like a male western box turtle, or another male Terepene species. It is most likely genetic because it is young. I can tell because the ridge on the carapace fades with age.
if it belonged to someone its overfed with high nutrients. if they have too much high nutrients cause they tryed to make it grow faster, the turtle gorws too fast and the shell cant keep up with its growth, causeing the turtle to die, or to have some internal problems. so the turtle it self grows faster than its shell.