Pakistan has put itself in the situation where literally anyone in the world can carry out terrorism within Pakistan. They don't even have to do it themselves; there are plenty of fanatics for hire within Pakistan who just need some money and a good pep talk to go and kill people. This bombing could have been indirectly 'sponsored' by Zimbabwe, for all we know.
When the government and army fail in their duty to ensure security within the country, it's open season for everyone.
The Pakistani generals don't seem to understand that, even if you are using guerillas as a tool of state policy, it is criminally insane to allow these lunatics to operate within your own country. India created and/or supported Mukhni Bharti, LTTE and BLA, but they didn't allow their Frankenstein to operate within India. As soon as LTTE deviated from the plot and started causing trouble in Tamil Nadu itself, the Indians went ballistic on their as$.
Just because you train a dog to hunt doesn't mean he should be doing it in your living room.