The new head of Britain’s foreign intelligence service MI6 will warn the nation that the “front line is everywhere” in her first public speech on Monday, as the UK faces emerging threats.

At about 4:20 p.m. on a cold Rhode Island Saturday, a message from Brown University flashed up on cellphones all over campus — everyone should run or take cover from an active shooter.

Australia already has some of the world’s toughest gun laws, but the Bondi mass shooting could lead to even tougher rules as the realization spreads that they aren’t strong enough to prevent bloodshed ...