A man has been arrested in connection with an IRA bomb attack that killed a Catholic nun and three PSNI officers in the North in 1990.
The 55-year-old was detained in Armagh on Thursday morning by detectives from the PSNI's Legacy Investigation Branch.
Sister Catherine Dunne, Constable William Hanson, Reserve Constable Joshua Willis and Reserve Constable David Sterritt were killed when a landmine exploded on the Killylea Road, Armagh on July 24, 1990. Another woman was also seriously injured in the blast.
PSNI Detective Inspector Deborah Eakin said the man has been arrested on suspicion of a number of offences including the four murders.
"He has been taken to the Serious Crime Suite at Musgrave Police Station in Belfast for questioning," she added.