John Boreland, a leading member of the Ulster Defence Association (UDA), a paramilitary group, was shot dead outside his home on Sunday night.
Police have called for calm and say they will increase patrols in the area.
Tensions among loyalist paramilitaries and criminality are among a number of lines of inquiry, police said.
But their early assessment is that this was not a sectarian murder.
The 46-year-old father-of-three was shot outside his flat in Sunningdale Gardens as he returned home just before 21:50 BST.
"He had just got out of his car when he was shot at close range a number of times," said the detective leading the investigation, Det Ch Insp Justyn Galloway.
"His injuries were such that he died at the scene."
Police believe a shotgun was used.
"John Boreland was known to police," said Mr Galloway. "He had survived a previous attempt on his life in 2014 and had been warned by police about his safety within the past few months."
The victim was being mourned by his two sons and his daughter, his fiancÃ©e, his sister and his mother and father, said Mr Galloway.
"I have visited the family today and I am sure you will understand that they are completely devastated," he added.
He appealed to the public for help in compiling information about the last 24 hours of Mr Boreland's life.
He also asked for anyone who witnessed vehicles leaving the scene of the shooting - including a motorbike, a silver Renault Megan car and a black Peugeot 307 car - to contact police.
North Belfast MP Nigel Dodds said the murder had "sent shockwaves throughout North Belfast and have cast a dark shadow over the local area".
Mr Dodds, who led a Democratic Unionist Party (DUP) delegation who met police to discuss the attack, welcomed the announcement that more police will be deployed in the area.
"We are committed to ensuring they have every resource necessary at their disposal during the investigation," said the DUP MP.
"We reiterate our calls to those who may have any information surrounding the events of last night to bring it forward to the PSNI as a matter of urgency."

Leicester Crown Court was told Iain Lawrence 53, of Ratcliffe Road, Leicester, had not come to terms with the break-up of his marriage.
The accident happened a day after an argument about finances involved in their upcoming divorce proceedings.
Mr Lawrence, who was not seriously injured in the crash, denies murder.
The court was told that Sally Lawrence's death was "a planned killing born out of grief, anger and jealousy".
Mrs Lawrence, 47, died from head injuries in the crash at Oadby in Leicestershire last October.
The court was told Mrs Lawrence's seatbelt had been unclipped before the crash and an airbag had been disabled.
The prosecution said the car had been driven deliberately into the tree with the passenger side taking the brunt of the impact.
The court also heard that Mrs Lawrence had often told relatives and friends that she was scared of her estranged husband.
The jury was told that police later found her car unlocked on the drive of the house with her handbag and overnight bag inside.
The trial continues.
A prominent loyalist who was murdered in north Belfast had been warned by police about his safety within the past few months, officers have confirmed.
[NEXT_CONCEPT]
A man deliberately crashed his car into a tree to kill his estranged wife who was travelling with him, a court has heard.