alt Hacker NewsIt says that the perp is Pakistani, and that he's been charged, but not that he's been arrested -- so he's presumably still free in Pakistan.
I hear that normally what the FBI would try in such cases is to lure people onto US or extraditable territory. IIRC there were some rogue Chinese chemists, who owned companies that sold fentanyl intermediates and were under secret indictment in the US, who were "invited to a VIP academic conference in Hawaii" and then arrested as soon as their flight landed.
Seems clear that this Pakistani is a bit more circumspect.
Most countries when presented with evidence that someone who lives there did something criminal will arrest and turn the criminal over to the country the crime was committed in. Sometimes they will put some stipulation in (Europe commonly won't turn a murderer over until the country promises not to seek the death penalty for example), but in general criminals are turned over all the time. In general a country doesn't want criminals living there even if the crime was done elsewhere and so they won't protect their own who commit a crime.
I don't know Pakistan's polices, but I would expect they would turn the criminal over to the US.