Why did God kill Uzza?


For touching the ark, while trying to keep it from falling

And when they came unto the threshingfloor of Chidon, Uzza put forth his hand to hold the ark; for the oxen stumbled.

And the anger of the LORD was kindled against Uzza, and he smote him, because he put his hand to the ark: and there he died before God. 1 Chronicles 13:9-10