BHC Design Engineer interview questions

First started with a phone interview with HR about background and qualifications. That went well then had in person interview. HR took me for a tour of the building and office. About 3 or 4 people interviewed for around 2 hours. Asked a lot of questions about previous projects from resume. Asked about what I would do in certain situations. Offered me the job then retracted it with out a given reason why. Very unprofessional.