It was the child holding a suppressed high-power rifle. 100% the suppressor.
I think I'm a bit older than you at 43. Suppressors for any firearm weren't even a thing that was available or popular when I was living close enough to home to get to regularly hunt... I think they might have been mostly illegal. Now, my cousins have suppressors on all sorts of rifles. They say its about protecting their ears, but I prefer my active noise cancelling muffs, and think they like suppressors mainly because they look cool.
In conclusion, if it were a pic of a 4 year old holding a Remington 870 Wingmaster or Express, I don't think I'd have thought anything other than "Awesome!"
I can argue with you or my cousins about the value of suppressors later if you want, but I don't want.
BTW, cute kid. He's got a very happy face.