You would do well to listen to this message. Really. Mahaney addresses the question we all have asked about Uzzah & others who were suddenly struck down by God. That is, "Why did God kill him?". I think you'll find the answer rather astonishing. It's a lengthy 60 minute message, but you won't notice. Just listen.
On a related note, I found the Mahaney message via this new mp3 sermon collection featuring preachers such as Mahaney, MacArthur, Piper, Carson and many more.