Reinstall Maverick but cannot access previous account

Hi all,

I have just inherited a 2011 Macbook Pro from a person who has unfortunately passed away and would like to start a clean reinstall of Maverick 10.9.5. However, the Macbook is still under the previous owners account and so when I go to reinstall Maverick via command&r, then select "reinstall os x" and then when I put my new account details in to sign in to the app store all I get is "This item is temporarily unavailable. Please try again later".

I have heard that one way round it is to go to "get online help" and open safari and try to sign into icloud, however when I try to load the icloud website that way the page will not load, all it does is keep refreshing itself in a loop as it tries to load.

Unfortunately, I do not know the password for the previous owners account nor do I have access to any email accounts of his to which it may be recovered.

Any ideas?

Thanks