On 25 October 1920, Sergeant Perry led a bicycle patrol of eight constables to investigate a case of malicious damage in Magherow. The group, which left Cliffoney barracks at 11.00 am, cycled into an ambush at Derry cross close to Ahamlish graveyard at 11.30 am. Some thirty to forty members of the North Sligo I.R.A., led by Liam Pilkington and Seamus Devins opened fire on the R.I.C., killing three instantly and wounding three more. The remaining three constables surrendered. Sergeant Patrick Perry, Constables Patrick Laffey and Patrick Keown died at the scene. Constables Lynch, Clarke and O'Rourke were wounded, with Patrick Lynch dying of his wounds that evening. Constables Spratt, McCormack and Joyce unhurt. "The three uninjured constables were deprived of their weapons and the weapons of the dead and wounded were collected. The ambushers then left the scene as the Angelus bell was ringing. One of the ambushers in fact had the job of ringing the bell and the ambush was over just in time to allow him to race across the fields to ring the bell at Grange church."