Islamabad, Pakistan (CNN) Khurram Zaki spent years denouncing Islamic extremists in his homeland. He apparently paid for it with his life.

The Pakistani human rights activist was gunned down at a restaurant in Karachi on Saturday night, fellow activist and lawyer Jibran Nasir said.

The Hakimullah faction of the Pakistani Taliban claimed responsibility for Zaki's death.

"Our four friends in Karachi riding on two motorcycles targeted Khurram Zaki successfully," faction spokesman Qari Saifullah said.