They've caught the perpetrator, the judicial process will run its course. I'm sure they are doing everything they can to find out if anyone else was involved in this attack.
National response has been appropriate. Gun laws have been been changed as of today and those changes have already received royal assent.
Playing the call to prayers over the national broadcasting service is unnecessary and over the top imo.
Ardern should back it off a bit now and get back to running her country.