RIP to the victims.
Looks like a well informed, planned, coordinated attack..someone internal information involved, made sure no security was around, took their time slowly executing the victims and easily got away.
Blaming external agencies - especially RAW is the easy way out, but it is most likely the output and an extension of the sectarian war between sunni extremists and the shias or vice versa in multiple countries. Shia vs Sunni war has a long history, plus, there is a global sunni jihad movement that calls to take up arms, send recruits and call for shariah all over the world, and pakistan being a partially radical society with ample availability of recruits, ideology and supporters - with a record of incidents of killing of shias for decades isn't exactly in need of any motivation from any external non muslim agency to kill a bus load of Shia. You have enough terrorist groups and people who would do that in a jiffy.
Why can't it be just one incident out of the centuries old shia sunni conflict instead of a conspiracy about something that even the extremists don't care about - like the chinese investment?.
P.S. If people here still think it's RAW and if one assumes that it indeed is them..then I would be astounded, astounded by the level of capability of RAW.If one believes all the so called Pakistani analysts writing furious columns or screaming on pakistani tv in paranoia claiming that RAW manages a mainstream pakistani political party, has control of your top TV and print media - GEO, Dawn, Express Tribune etc or proclaiming that RAW has 30,000 agents operating inside pakistan. Not to forget RAW controlling a few of pakistan's top terrorist and political organizations - TTP, MQM, BLA, BLM etc etc.....even zardari and nawaz have been blamed as Indian pittos...astounding indeed.