Employment Based Greencard

I had EB2 (NIW) interview yesterday at Atlanta field office. I went with my wife and our five year old son as dependents. The IO was very friendly but the Ys/No questions for both of us were very boring. The IO checked a few of our documents, collected some family photos, and made copies of our DL and land title registration. They then took our our pictures and FPs. They asked if we had any question for them and we said no, and they indicated they would run another background check and adjudicate on the case. The interview was over. I was really confused because I was expecting some questions about my education, research, etc. It appears the IO had no doubt about our relationship but they indicated that they just needed documents that can justify their decision, should they be questioned about their decision. At the end, we were escorted out of the office. We were not given any letter. I don't know if this is normal.