Why Klay returned briefly to shoot the FTs:
"Section II—Shooting of Free Throw
The free throw(s) awarded because of a personal foul shall be attempted by the offended player.
EXCEPTIONS:
If the offended player is injured, other than as a result of a flagrant foul or unsportsmanlike conduct, or is ejected from the game and cannot attempt the awarded free throw(s), the opposing coach shall select, from his opponent’s bench, the replacement player. That player will attempt the free throw(s) and the injured player will not be permitted to re-enter the game. The substitute must remain in the game until the ball is legally touched by a player on the court."