Response of Shady Crooks
The con artists of the wizarding world, ever ready to make a quick sickle from an unsuspecting mark, start spreading rumours that St Mungo's is full to capacity and is only treating seriously injured casualties. They offer their services to injured civilians, for a small price of course, to cover the cost of potions.
They also start offering a protective charm service, where they apply a charm that magically repels muggle weapons and keeps you perfectly safe, guv'nor.
The majority of these shady back-alley clinics spring up in Diagon and Knockturn Alley, with a few loitering in Hogsmeade for the worried and gullible student.