We emigrated to Canada when I was 9, and my mother immediately started working 2 jobs to support us.
I was a "latchkey kid" from 9 up. I even kept my housekey on a string around my neck, like lots of other kids in the seventies and eighties.
(BTW - molestations, rapes and kidnappings peaked in the seventies and have been falling steadily ever since, so it was a LOT more dangerous when I was a kid, than it is now.)
I was supposed to stay home and wait for my mother to get off work, but one day when I was 10 I decided I had enough time to catch a bus across town to the toystore and get back without my mother ever finding out.
Except I got hit by a car, while running across the street to catch the bus. Totally my fault, and I got the skin scraped off from my knees to my toes. Ouch! The cops put iodine and bandaids on, and then took me home. Where I flatly refused to tell them how to contact my mother, because I knew I was going to be in trouble.
Of course, they finally got it out of me, and my mom came rushing home from work in a panic. They told her that they'd let it pass this time, because there was food in the fridge and I was obviously well cared for, but that it was illegal to allow a child under age 12 to be left unsupervised.
Of course, that was the same night that the neighbour - seeing a cop car outside our house - decided to drop by and inform my mother that I'd been setting little fires in the alley.
Yeah, it wasn't a pretty picture at our home that night.
So... when my kids were 8 and 10, I would leave them to say, run to the corner store for 10 or 15 minutes, but no longer. And the corner store is in direct line of sight from our house.
Kids are idiots. You leave them alone too long and they get up to stuff. I started leaving them slightly longer (an hour or so) when they were 10 and 12, but then they were always in each other's company and I could trust that they'd keep an eye on each other. And happily rat each other out, if they stepped out of line.
My son is 12 now and I feel perfectly confident to leave him alone in the house for a few hours. He's proven himself reliable and sensible and capable of putting out small fires with a box of baking soda.
My daughter is 14 and currently touring Europe with her grandmother. She's not quite so reliable as her brother and has already managed to lose her wallet, but luckily a shopkeeper found it and she should be getting it back today, before they leave for France.
So... about the 8yo? 1. It depends on the local laws. 2. It depends on the child. 3. Generally, I'd say an 8yo by himself should not be left alone for more than a few minutes, but if he's with older siblings, it's probably okay.