We recently hired an Account Manager to work remotely. We are in Philadelphia and he is in Chicago. He worked for 3 days and now is not responding to any of our calls/emails. It's been 1 week since we have heard from him. Can we terminate him

We recently hired an Account Manager to work remotely. We are in Philadelphia and he is in Chicago. He worked for 3 days and now is not responding to any of our calls/emails. It's been 1 week since we have heard from him. Can we terminate him by a letter and, since we sent him a laptop computer, how do we get that back? Thanks