Superintendent Kevin English said the gang who killed father-of-two Andrew Allen must have used a second car.
Mr Allen, 24, was shot several times and killed at his home at Links View Park in Lisfannon on Thursday night.
The three man gang, who carried out the attack, escaped in a silver Vauxhall Cavalier which they later burned out at Ballyhone in Fahan.
Supt English appealed to members of the pubic who may have noticed a car parked close to Church Brae, Fahan where’s the gang’s original car was set on fire, to contact Gardai.
“Somebody may have seen this second car that was left or persons who were acting suspiciously. We would ask anyone to contact the incident room in Buncrana,” he said.
A press conference at Buncrana Garda station this afternoon heard
the gang had tried to force their way into his house before shooting several shots into a downstairs bedroom.
Gardai revealed the front door of the house at Links View Park in Buncrana was locked when the three armed and masked men called at 9.30pm on Thursday evening.
At least one member of the gang shot several shots into the left downstairs bedroom of the house killing the 24 year old father-of-two.
It is believed he was hit a number of times before he fell to the bedroom floor.
Mr Allen, who had moved from the Top of The Hill on the Waterside area of Derry six months ago was pronounced dead at the scene.
The dead man’s girlfriend was in the house at the time of the attack but was uninjured.
The entire attack took just a number of seconds before the men made their getaway.
Several members of the dead man’s family left bunches of flowers at the Garda cordon yesterday afternoon.
The State Pathologist arrived at the murder scene yesterday and Mr Allen’s body was due to be removed to Letterkenny General Hospital last night.
No organization has yet claimed any responsibility for the killing.
However it is understood the Republican Action Against Drugs group issued death threats to Mr Allen and a number of other men in Derry several months ago.