Something must be done
Something must be done, and getting a law passed that the FBI can unlock iPhones is the least we can do.
I don't see why you got down-voted for this, since that's _exactly_ the sort of thing that happens in these cases. Any restrictions on military-grade firearms (the one thing that _would_ help) is right out, so the FBI might as well pick some totally unrelated goal they want to achieve and try to get some mileage towards that.
Somewhere, somebody is probably trying to use this mass shooting to justify passing a law to persecute LGBT people, immigrants, scientists, etc.