Cannot delete contact from Address Book

I have a particular contact I cannot delete from Address Book. There was a birthday event in calendar for a person I didn't recognize, so I tried to delete it. However, Calendar said that I needed to delete it from Contacts, so I opened Address Book and tried to delete the contact. Right-clicking on the contact's name did not list the option to delete it, the delete card option was grayed out in the Edit menu, and command+delete just make the computer beep. I found [this page](https://discussions.apple.com/thread/5011903?tstart=0) with the below command to try. { sudo chflags -R nouchg,nouappnd ~ $TMPDIR.. ; sudo chown -R $UID:staff ~ $_ ; sudo chmod -R u+rwX ~ $_ ; chmod -R -N ~ $_ ; } 2> /dev/null It looks like it goes through and changes the ownership of all your files to make sure they're actually yours. Should I try this solution, or is there a better option to let me delete the unnecessary contact? I'm running El Capitan, in case that makes the instructions any different.