Police now say at least seven people were killed in a grisly, execution-style shooting in Pakistan. Another was critically injured.

Authorities say the victims were tied to chairs with their hands behind their backs and their mouths taped before being shot point-blank in the head. The shootings took place at the offices of the Institute for Peace and Justice, a Pakistani Christian charity that does work in Karachi. All seven of the dead are identified as Pakistani Christians.

Police say an office assistant who was tied up and beaten by the attackers says two gunmen did the shooting. Investigators still want to know how the gunmen got into the office, which had an electronic door that could only be opened from the inside.

The shooting is the latest in a series of attacks against Christians and Westerners, who have been increasingly targeted following Pakistan's move to crack down on Islamic militant groups.