It does look like a deer mouse. They can contain hantavirus which is a very dangerous disease. That one looks old enough to release in my opinion by the way.

http://www.nlm.nih.gov/medlineplus/ency/...

http://www.animalspot.net/deer-mouse.htm...

http://denver.cbslocal.com/2014/08/05/he...

It might have rabies. You'd be better off buying a mouse at a pet store.