This article contains plot spoilers for the 2017 series of Twin Peaks.
The boy was looking out his window at Dougie Jones' car on the other side of the street. While watching, he noticed Gene place a bomb on the car. The boy didn't seem to have any reaction to his drug addled mother, who was shouting "one one nine" repeatedly.
Later, when his mother was passed out, the boy went across the street to inspect Dougie's car. Before he was able to set off the bomb, three delinquents shooed him away and tried to hijack the car, and end up setting off the bomb. The boy then ran back inside his home, waking his mother in the process.