Dissident republican bombers have struck twice in recent weeks.
On Saturday a bomb exploded at Dunmurry PSNI station in Belfast.
The bombers used an almost identical method to those who tried to attack Lurgan police station last month.
In both attacks a delivery driver was hijacked, threatened, and told to drive the bomb to its target.
These attacks, claimed by the New IRA, came after a lull in violence– so what has sparked this outbreak?
Ciarán Dunbar is joined by Belfast Telegraph security correspondent, Allison Morris.