chick mysteriously died?!

[WolfenKitty]

So I have these 2 light brahma chickens, and i put both of them in the garage for only 2 hours or so, but one just mysteriously dies when I got back. I only have two chickens, and I am new to chicken owning, and I am afraid that my other one would die. Please help!

 

[lightchick]

Did they act weird or anything?

 

[Ol Grey Mare]

How old are your chicks? How were they kept while in the garage?

 

[WolfenKitty]

They weren't acting weird in any way, and I put them in a temp. Cardboard brooder box. It was pretty warm so I didn't use the heat lamp. They are about three weeks old.