Mongo DB failed to start. Failed to lock file: /data/db/mongod.lock The resource is temporarily unavailable

I have installed MongoDB with Homebrew. I also created the / data / db directory.

However, when I start mongod I get this message:

exception in initAndListen: 98 Unable to lock file: /data/db/mongod.lock Resource temporarily unavailable. Is a mongod instance already running?, terminating

      

        
        
        
      

    

I doubt it is already running because I just installed it. I quit terminal and rebooted but it doesn't help.

Here is a screenshot of my terminal

Any idea what I need to do? Thank!