Jason McGovern, 19, was injured in two separate attacks in Omagh. At around 2am he was assaulted after an altercation with a large group of people at the Terrace Bar on John Street.
Minutes later he was punched in the face at the nearby Kelvin Road, close to the Weigh Inn bar.
Mr McGovern fell to the ground and was left unconscious after the second attack. He was then helped into a taxi and taken to his friend's house at Emyvale, Co Monaghan.
Mr McGovern was found dead in bed on Monday 31 December at around noon.
A 21-year-old man was arrested on Monday by police investigating the murder. He has been released on bail pending further inquiries.
Four men and one youth have been charged with affray in connection with the death.