Is it Illegal?

So there's a Mexican family that lives across the street from me. They have a young child. I'd guess he's 4 or 5. I don't think he was in school last Winter or Spring. Of course the family could be illegal.... but I think I am ok at guessing kids ages these days. So this kid mows his lawn, very regularly. Assuming he's 5, is this legal? What is the proper age that a kid can start mowing lawns? I'd think it's older than 5. He's also not supervised. Like if the Dad was standing right there, ok. But this kid mows the lawn while his Dad is at work (assuming) and Mom is inside. So last week, he mows the lawn then when he's finished he starts shooting off firecrackers. Paul witnesses this and texts me, "So the kid across the street finished mowing the lawn, now he's shooting off firecrackers... should I go over there and offer him a beer and a cigarette?"
Funny or scary? Do I call the cops before something tragic happens? I want to get a picture one day.

*UPDATE*
So when I finished writing this I felt the need to google proper lawn mowing safety. I found this, I am only posting the first 4, the rest are irrelevant to my blog.

The ASRM, ASPS, AAP and AAOS offer the following tips to help prevent lawn mower-related injuries:

• Children should be at least 12 years old before they operate any lawn mower, and at least 16 years old for a ride-on mower.

• Children should never be passengers on ride-on mowers.

• Always wear sturdy shoes while mowing -- not sandals.

• Young children should be a safe distance from the area you are mowing.