Who are these people?

Like I said, it is very common everywhere to burn and torch vehicles after any major incident.
This particular attack on KFC may have been from anti-American zealots like those from Jamat i Islami. Who knows?

http://www.onlinenews.com.pk/details.php?id=150293
On Monday morning when the news of Haideri’s killing broke out, enraged crowds of his followers came on streets in various cities including Karachi, Hyderabad, Sukkur, Khairpur, Checha Watni and hurled stones on the vehicles.

The angry mob also set a bus and vehicle set on fire in Nagan Chowrangi area of Karachi. Due to firing of unidentified men, the vehicle of fire brigade could not be reached in the area to extinguish the fire.

The shopkeepers had to shut their shops and business activities after incidents of firing in North Karachi, Nagan Chowrangi, North Naziamabad and Quaid-e-Abad areas while the business activities could not be started in various areas of Karachi.

http://www.reuters.com/article/idUSCOL329830._CH_.2400
Officials said rioters had burned hundreds of vehicles and shops as well dozens of banks and petrol stations across the country, with much of the damage in Sindh.

A leather factory was reportedly burnt by miscreants but nobody was reported hurt in New Karachi. In Saddar Town, 31 shops were looted and burnt