Time bomb

Aftermath of the bombing at the Bologna railway station in August 1980 which killed 85 people, the deadliest event during the Years of Lead.
Aftermath of the Grand Hotel bombing in Brighton (1984) which was targeted at British Prime Minister Margaret Thatcher, the result of a time bomb which had been placed in the hotel nearly a month before it detonated. Thatcher wasn't harmed, but five others were killed and 31 were injured.

A time bomb (also known as a timebomb or time-bomb) is a bomb whose detonation is triggered by a timer. The use or attempted use of time bombs has been for various purposes including insurance fraud, terrorism, assassination, sabotage and warfare. They are a frequent plot device in thriller and action films as they offer a way of imparting a dramatic sense of urgency.

Aftermath of the Deal barracks bombing, which killed 11 people in September 1989.