The ice he's standing on could easily still be thick enough to hold a small vehicle, ice is far stronger than most people realize, generally when ice opens up it's not because of something on top of it necessarily, there's usually already a crack or something that was pushed by something on top, holes also open up seemingly at random all the time, particularly on larger lakes, you'll be out on the ice and hear what sounds like an explosion in the distance and see a large whole open up(my dad saw one open up about 100 feet from a dude who drove his truck out onto the ice, dude was shook), large cracks will also often be quite loud, but are generally harmless