I had one in-person interview at their Houston office. It went well and they offered me the job by phone a few days later. I was considering another offer at the time and asked for a written offer letter and a few more days to decide. The manager then called me back to say they were withdrawing the offer as they needed someone immediately. I was a new grad and pretty naive at the time, but even then I knew it was a big red flag and very unprofessional.