What were they thinking?

I have to share what happened to me yesterday. It was about 5:30 pm and I was making Bryce some cereal, and I was about to set him down on the carpet in the living room and the front door opened a little. So I looked over at it and it shut by itself. Now I am a pretty paranoid person normally and this would have really freaked me out but I was relatively calm. I walked over to the door and peaked out the peep hole. I saw some people standing in the street and I thought that maybe they were just delivering things on the door knob. Sometimes the door doesn't latch all the way and I thought that maybe they pushed on the door and it opened slightly. So I went to get the rest of Bryce's food and thought I need to look out the peep whole one last time. As I did there was this woman with her daughter walking to the front door. I stepped back for a minute because I thought that maybe she was going to knock and I didn't want it to startle me. As I did that the door opened. I was kind of startled at first and then I grabbed the door and opened it. My initial thought was that maybe they just forgot and walked into the wrong house. And then she started to talk. She said "I saw that the house was for sale and we noticed that it was unlocked, we were going to come in and look around" I am sure that I had that your stupid look on my face and said, "this is my house and I live here, if you want to come in and look at it you are going to have to call the number on the sign and make an appointment." she said "oh". I was stunned. Who thinks that they can just go into unlocked homes like that and not think that there is some one living in there. Are people really that stupid? This is TEXAS, we could have guns, they could get shot for doing something like that. What were they thinking?