What chilling discovery does Malala make in early 2012?

In Chapter Eighteen, we learn that Malala and her family were visiting relatives in Karachi (2012). During that trip the family visited a school named in her honor, where they learned of a threat on against Malala on the internet. The threat claimed Malala was “spreading secularism and should be killed.” They also learned that the Swat police wanted to talk to Malala's father as soon as they returned home.