mouse care

Hi, I just found my cat hanging with this little mouse. I've looked and think it's a deer mouse but am totally unsure! I'm also unsure of his age or how to proceed with care. Any help would seriously be greatly GREATLY appreciated.

Hello, everyone. I have taken an interest in mice... When I went to Petsmart I saw this beautiful male with a black and white face. And when I put my finger on the glass, his paw did the same. :] I know he's the one for me. I'm in the process of convincing my parents to let me buy him. I know, I...