Newbie Admin.

I have recently inherited a Linux server running pgsql and need to lock someone out but have so far been unsuccessful.

I have changed the Linux passwords

I have changed the passwords on the 3 users listed on the Database

Now the problem is the person (server) I need to block access can still connect to the database.  I have verified this by changing a record in the database and the changes were reflected on the other server.  I looked for pg_hba.conf and there isn’t one that I can find so I am wondering if it is a persistent connection and if it is how do I kill it?  Will restarting the server drop the connection?