George Brown, 52, from Ballygawley Road in Aghadowey appeared in the dock of Coleraine Crown Court, sitting in Belfast, where he pleaded guilty to unlawfully killing Neil McFerran and Aaron Davidson.The families of both young men were in the public gallery to hear the gas fitter admit his responsibility for their deaths.The 18-year old friends died of carbon monoxide poisoning after they were overcome by the deadly gas in a holiday apartment in Castlerock on 3 August 2010.The pair - who along with another friend had gone to the seaside town for a break ahead of getting their A Level results - were found by their parents, who rushed from their homes in Newtowabbey to Castlerock when they were unable to contact them on the phone.Brown initially denied two charges of manslaughter and a trial was due to commence next week.However, he was re-arraigned on a total of 21 charges and on Tuesday pleaded guilty to of all of them.As well as the two manslaughter charges, Brown admitted a string of offences involving failures in health and safety legislation.These charges include 15 counts of failing to protect non-employees, failing to ensure those fitting gas appliances were qualified and failing to test whether appliances were correctly connected.The charges relate not just to the holiday home in Castlerock where Neil and Aaron perished, but also other private properties as well as a restaurant and caravan park in Coleraine.This is the first conviction in Northern Ireland for manslaughter by gross negligence as a result of carbon monoxide poisoning.Chief Inspector Rachel ShieldsAfter Brown pleaded guilty to all 21 charges, crown prosecutor Frank O'Donoghoe QC told Mr Justice Weir: "This is a case where victim impact reports will be obtained in respect of the families of the two deceased, and of a third young man who was seriously injured in this tragic incident."Brown's barrister, Jonpaul Shields, confirmed pre-sentence reports would also be sought on behalf of his client.Police have welcomed Brown's guilty plea.Chief Inspector Rachel Shields said: "The Police Service of Northern Ireland has worked closely with the Health and Safety Executive and the families and friends of Aaron and Neil to bring this case before the courts."Aaron and Neil's deaths were tragic and prompted a wide-scale rigorous investigation on 3rd August 2010, involving members of the Health and Safety Executive NI's Gas Safety Inspection team, its Major Investigations Team, its Scientific Services Unit and officers from the PSNI's Criminal Investigation Department."This investigation culminated in today's guilty plea. Over the course of the last three years, the families of Aaron and Neil have sought to highlight the issue of carbon monoxide poisoning."It is an issue that all households should be aware of and I would remind service providers who work with installing heating systems or maintaining heating systems of the legal requirements and responsibilities that govern this area of business."Brown will be sentenced for the offences on 14 March. He was released on continuing bail by Mr Justice Weir.