Oh man, I'm about to write you a book, lol!
First off, what kind of chameleon was it and what kind does he want to get this time? There are tons of kinds and they require very different temps and humidity...
I was researching chameleons for months before I got mine and I'm still a little worried for her! I don't know what kind of cham you're thinking of, so I don't know specific temps, but in general they need a heat gradient. They need a heat lamp pointing at a basking spot (hottest spot in thier cage) and cooler areas to go to if they get too warm. They also need a UV light (zoomed 5.0 is a highly reccomended one) that they can be within 12 inches from. Also, chameleons don't do well in glass enclosures because some (possibly all) are solitary and will try to fight with thier reflection, they won't know that there is a wall there and will keep trying to climb through it and stress themselves out, and they don't have very good ventilation. They also need LOTS of stuff to climb on since they will spend all thier time in the branches, and they need a mister or drip system (or you can do it manually) to get thier water, from everything I've read, most chameleons will not drink out of a bowl of still water (they need the drips to catch thier attention. Have your brother look for care sheets online of the specific type of chameleon he wants to get the right temps and humidity levels, my advice is to get the whole setup in order lights heat and all, make sure you can keep them at the right levels, and THEN go get the chameleon. A good setup can be expensive! My chameleon was given to me, but I wound up spending over $100 putting together a decent enclosure.
There were a lot of things that could have happened to the other chameleon, could have been the temperatures, he could have been sick when he came to you... no telling
In case you couldn't tell, I just got my cham and I'm chock full of research material
If there's anything else I can help with, I'd love too! Another member (Ravnos) is very knowledgeable about herps too, I'm sure he'll be around!