Original sentence: Sir Norman was killed aged 86, alongside his son James, in the library of their home, Tynan Abbey, on the evening of 21 January 1981, by members of the Provisional Irish Republican Army, armed with machine guns and grenades
Edited sentence: Sir Norman was killed aged 86, alongside his son James, in the library of their home, Tynan Abbey, on the evening of 21 January 1981, by members of the Provisional Irish Republican Army, a proscribed organisation, armed with (illegally held) machine guns and grenades