Suspicion for this morning's shooting of William Stobie is centring on his former associates in the Ulster Defence Association.
It is understood Stobie, who was recently cleared of the murder of solicitor Pat Finucane in 1989, had been warned by police within the last 10 days that his life was under threat.
He had been assured by loyalists in the area in which he lived that he would not be harmed.
Stobie died after he was shot as he approached his car outside his flat in the staunchly loyalist Glencairn estate in north Belfast at around 6.15am.
The gunmen had apparently being lying in wait for him.
He was hit several times at close range.