Police have made a fresh appeal to help catch whoever attacked a teenager who died on New Year's Eve.
Jason McGovern was found dead on Monday after being assaulted twice in Omagh.
Five men and a teenager have been charged with affray in connection with the incident, which happened at around 2am on John Street and Kevlin Road.
Detective Chief Inspector Richard Harkness, from the PSNI's Serious Crime Branch, said the assistance of local people will be vital in bringing those responsible for Jason's murder before the courts.
"We have made a number of arrests but this investigation will continue for some time and we are asking for people's assistance about information surrounding the events that led to Jason's death," he said.
"There were a large number of people socialising in the area at the time of the assault and also a number of motorists in the area of John Street and Kevlin Road.
"I have a specific appeal to any pedestrians or motorists who were in the area of the Terrace Bar or Sally O'Brien's nightclub in John Street Omagh at approximately 1.55am and witnessed the assault on Mr McGovern and his friend, or a short time later at the Weigh Inn car park at Kevlin Road and witnessed Mr McGovern being assaulted for a second time to come forward and speak to police if they have not already done so."
Mr McGovern travelled to Omagh with a group of friends but became separated. He was punched outside a nightclub after being involved in a verbal exchange with a group of men.
He later made his way to the border village of Emyvale, Co Monaghan, where he had been staying with friends and was found dead at midday on New Years Eve.
Senior officers from PSNI's Serious Crime Branch made the appeal for information exactly one week from his death.