Little boys that age are obsessed with police and common delivery people -- he would know those uniforms and that is what he would call the person -- not "man in black," but "the police" or "the mail man." Also, since people (especially young men) DO wear a lot of black and dark colors, this had to be something that really stood out to him -- something he had no words for. Like something wrapped around his head as a mask, or some other bizarre get-up. As for why he would not scream out or react....depends on what he was used to in the home. Some homes do have a lot of people in and out, including overnight guests, so the child may not be shocked to see a person in the middle of the night so long as that person does not appear threatening. Also, if Haleigh seemed calm, then her little brother would have taken the cue from her.
But it's amazing what kids will accept as normal. You really can't expect them to apply the same standards to judge a situation as an adult would apply. When I was a small child, my bedroom was next to our neighbor's house, but my parents' bedroom was all the way on the other side of the house. Nobody had AC, so in the spring/summer, windows would be left open. There was an evolving domestic situation in my neighbor's house which nobody knew about (nothing that constituted abuse of the children -- it was more that an adult in the home was beginning to suffer a breakdown, and the early episodes seemed to occur late at night). In the middle of the night, I used to hear screaming, crying and bizarre things getting yelled out. I was about 3-4 at the time. My parents had no clue what was going on until eventually it became well known in the neighborhood and the person's condition deteriorated so that these things happened in the daytime as well. But at around this time, my parents remember I had a habit of sleepwalking and coming into their room late at night and trying to sleep with them. However, I never once told them the stuff I was hearing.
I think children are still developing a sense of the world around them, what is normal and what is not normal, and they frequently assess situations based on whether there is an actual threat, based on what they SEE and not based on some general societal concept of a threat (i.e., is the man in your bedroom a threat because he is growling at you and holding up a knife, or is he a threat because you know from reading the news and living in our society that even the gentlest seeming man is not supposed to be in your bedroom?!?!), and then, if there is a threat, I think they often respond with actions and not with words, because they are biologically hard-wired with a "fight or flight" response.
