Serbian police shoot dead attacker outside Israeli embassy in Belgrade

Serbian police shot dead a young man outside the Israeli embassy in Belgrade early Wednesday after what authorities called a "terrorist attack"; Interior Minister Ivica Dacic said the attacker, a Serbian minor already monitored by security services, rushed an officer with two knives, and he raised the terrorism threat level to "red alert". BBC News

BBC NewsSerbian shot dead after attacking officer outside Israeli embassy, minister saysAuthorities say the attacker in Belgrade was an underage male who was being monitored by security services.

How should security services handle minors they already know to be following extremist groups online?