Can a user be put into multiple SharePoint groups

Hi,

I have a domainuser who is in the Site owner Sharepoint group. Now, I am adding domain\Users which includes all the users including the one I added earlier to the SharePoint visitors group. Can this user be in two SharePoint groups at the same time and what permissions would he inherit ?

The requirement is to give read permissions to all domain users using domain\Users and give this user Owner priviliges as well.

Cheers,

Amit