Does Houston have their own set of codes? What you might do is look at a copy of "Police Call" magazine at your closest Radio Shack store. Towards the back of the book they show district maps and department-specific 10 codes of selected cities and agencies. I THINK that I've Houston's on there. Either way, it would be worth a look. If they use the APCO 10-codes, then a 10-50 is a motor vehicle accident and then they should specify with or without injuries, fatality,etc. In Odessa, a major accident is a 10-150, and any fatality or dead body is a 10-118.
There was a story on the TV news a couple of weeks ago that stated that anyone receiving any sort of federal funds would now have to scrap all of their 10-codes in favor of "plain language" transmissions. You couldn't say 10-4 any more only affirmative or acknowledged. I don't remember what the deadline for implementation is but it's going to be interesting to see how it goes.