The policeman that talked to H, the girls, and B (ex-sis-in-law's boyfriend) was very impressed with H and told him he did exactly the right thing. H said he just wanted to make sure the two girls were safe.
I don't know if they caught the guy or not (I'm sure they would have mentioned it to my mom if the guy had), but I doubt that they'll be leaving the kids alone like that for a while despite the fact they actually live in a very nice middle-income neighborhood. I don't believe the guy got in. He probably heard the noise that they were making suddenly stop and figured out that it wasn't a good idea to keep trying to get in.
I have always known that my nephew was smart, but I am frelling PROUD of him for keeping cool in a damn dangerous situation and looking out for the little ones. He'll be 14 in a couple weeks. H has always thought of things a bit differently than other kids, and that was probably the factor that let him do the right things without panicking. (he has a tendency to freak us out with serious philosophical questions about religion, the afterlife, and human nature as I've mentioned here from time to time.)
That's my baby boy!
H and his sister, V, last year.