Thunder v Spurs

[OfficialBFish]

Late in first quarter Durant fouls Ginobili on the way down on a three point attempt. At seemingly the same time, David West fouls Kanter while ball is in flight. Officials go to the replay, and in replay it appears that the foul on West did occur a bit after Durants foul. Officials end up ruling that West's foul was technical and Ginobli will also have three free throws. Can anyone clear up exactly what the happened here, specifically everything that the referees needed to look for in replay, and what if anything would change if the game was under NFHS rules? If anyone has video that would help too