What would you do? Parents leave children unattended

So I was leaving my house and a brother and sister on our street were just walking along the street. They’re friends with my son as far as just playing outside. So I asked if they missed the bus because it was an hour after the bus and I know dad works. The girl said her dad told them to stay home today. I was thinking maybe he got the days of school mixed up but I said I know school is cancelled on Monday but not today. She said she doesn’t know where her dad is but he said to stay home because they go to San Antonio today. I asked if they were ok and she said yes.

So the girl clearly has no idea where he is and I’m not even sure if he just left them overnight by themselves... the girl is in 3rd and the boy is in 1st. So I started driving and felt kind of weird just leaving them. So I’ve notified the school and they’re trying to get in contact with the father now. I’m sure he’ll be pissed that I didn’t mind my own business but oh well. His kids are always wandering the streets and I rarely see the guy. I’m curious now how often they’re being left alone. 🤔

What would you have done? I’m not sure what the legal age is to leave a child by themselves but I feel like that’s too young. Especially if you aren’t staying inside the house.