Who was Uzzah?
Uzzah was one of those who accompanied the ark on its journey from Kiriath-jearim toward David's citadel (2 Samuel 6:3-8 , "Uzzah" = 1 Chronicles 13:7-11 , "Uzza"). From the text of 2 Samuel 6:3-8 , as generally corrected with the help of Septuagint, it is supposed that Uzzah walked by the side of the ark while Ahio (or "his brother") went in front of it.
The word which describes what happened to the oxen is variously translated; the Revised Version (British and American) has "stumbled"; others render it, "They let the oxen slip," "The oxen shook (the ark)."
Uzzah, whatever it be that took place, caught hold of the ark; something else happened, and Uzzah died on the spot. If the word translated "rashness" (Revised Version margin) in 2 Samuel 6:7 (not "error" as English Versions of the Bible) is to be kept in the text, Uzzah would be considered guilty of too little reverence for the ark; but the words "for (his) rashness" are lacking in the Septuagint (Codex Vaticanus), while 1 Chronicles 13:10 has "because he put forth his hand to the ark," and further no such Hebrew word as we find here is known to us.
The older commentators regarded the death as provoked by non-observance of the provisions about the ark as given in the Pentateuch, but it is generally believed today that these were not known in David's time.
What is clear is that Uzzah's act led to an accident of some kind, and the event was regarded by David as inauspicious, so that the journey with the ark was discontinued. We know how the Old Testament writers represent events as due to divine intervention where we would perhaps discern natural causes.
IBSE, "Isaac" (in the public domain) with minor edits.