I hate to say it, and not to scare you, but they look an AWFUL lot like pictures I just saw on facebook the other day... someone discovered some similar looking bugs on some clothing they were looking at, at walmart...... Bedbugs :nightmare:... I sure hope that's not what they are!
apparently they can vary in size according to stage, adults can be as big as a sesame seed.
I did some googling and found some pics... look pretty similar, If he sees them outside of his garage, it could be possible a neighbor threw away an infested bed or piece of furniture?
ALTHOUGH, the antennae do look longer in his pics.
best bet would be to put to put one a bag and show an exterminator, They can identify if its a pest or not.