initially up until 2008, MQM and -H were doing the killings.
Then MQM saw Pathans and Baloch (B/P) growing over 18 and saw losing vote banks because Bloch and Pathans werent MQMers, so MQM started killing pathans. The killings were actually meant to be force to drive out B/P people of the MQM strongholds.
MQM elites underestimated pathans, then Pathans had to protect themselves and get even, so they started attacking MQM. hence the mess we are in now
by the way, Syed Shahi seems to have disappeared these days