Rans Enduro Sport, Hase Kettweisel Tandem, Merin Bear Valley beater bike
If you pull back the rubber hood from the top you will find a little groove where a 5mm allen wrench can fit in to loosen the clamp. When you go to retighten it, don't go overboard. If your son crashes again (as is likely) you'd rather the brifters give a little rather than break. The brifters are one of the more costly components to replace.
'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
The clamp bolts are outboard of the shifter body on the outside face. As RG said, look at the shifters and you will see a groove disappearing under the rubber hoods. A 5 mm allan wrench wiggled down that groove will find the fastening bolt.