Actually, they don't. They have a legal system with an Islamic bent, but it's not Sharia. I was surprised to learn that every time there's been a free election, Pakistanis have overwhelmingly rejected Islamic parties and voted for secular types.
The Army has always been fanatically anti-Islamist and hasn't been shy about waving the big stick when allowed. 8 dead in this affair is small beer compared to operations in Waziristan over the last couple of years.