The 61-year-old fell 50ft to his death trying to escape from Ballymena flat on on Friday night
The criminal, an associate of exiled former UDA chief Dee Coleman, may have believed a gang was entering the block of apartments to take his life.
After Johnston’s death, his solicitor, Ciarán Shiels, said some charges Johnston had been facing were expected to be dropped.
He said the family of the deceased believe Johnston may have tried to escape from the block of flats because he believed his life to be at risk.
Mr Shiels said his client had “received various threat notifications over the years” and the most likely explanation for Johnston trying to climb outside the window and onto a drain pipe was because he thought he was “going to be shot”.
The Police Ombudsman has since started an investigation into the incident.
Mr Shiels said his client had never been arrested in connection to heroin dealing, further claiming Johnston, who had been facing fraud charges, wasn’t involved in heroin dealing, even though he had a conviction for dealing in cannabis, and that “nobody was trying to pull the wool over people’s eyes” in regards to Johnston’s background.
Johnston’ funeral took place this morning in Ballymena at his daughter’s house, followed by interment at Ballymena Cemetery.
In an article published after Johnston’s death, Belfast Telegraph journalist John Laverty, who went to school with him, described the drug dealer as being a “shy and reserved” boy who later developed a fearsome reputation as a “hard-man”, becoming a nightclub bouncer; a job which would later lead to him becoming involved in the drugs underworld where he would be branded a ‘Cocaine King’.
The 61-year-old convicted dealer plunged 50ft to his death in Ballymena on Friday night.
Locals say Johnston attempted to escape out a window of an apartment block as riot-clad cops sledge-hammered their way into a flat where a suspected party was in full swing.
It is believed he stood on a ledge for only a few seconds before falling to his death.
A neighbour - who had known Johnston since childhood - found the dying drugs boss at around 6.45pm.
He told the Sunday World: "I was walking the dog in the car park when I heard a heavy thud around the corner. It was followed by a low moaning sound.
"I raced over and saw a man lying on the ground next to a manhole cover. I recognised him right away and I knew it was Noel Johnston. We live next to each other.
"He was dead as soon as he hit the ground.
"I knew there was nothing could be done to save Noel. I was in a state of shock afterwards.
"I hadn't taken a drink for two years, but as soon as I got up into my flat, I poured myself a large vodka and Lucozade. I needed something to calm me," he said.
"I never seen anything like that in my life before and I hope I never see it again."
The man also praised the efforts of the police and emergency services who worked tirelessly for over an hour in an attempt to save Johnston's life.
"They did everything possible. A saw a young female police officer pounding Noel's chest. She was trying to bring him round.
"Paramedics even used electric shock treatment on his body. But it was no use. Noel was gone, that was obvious. It was an awful sight," he said.
Johnston is credited with introducing heroin to the streets of the Co Antrim market town and indeed to Northern Ireland.
In the 1990s - under Johnston's vice-like control - Ballymena became a Mecca for dealers and dope heads across the North.
Heroin heads from Belfast even jumped the train to Ballymena where they knew they could safely score the highly addictive 'dirty drug', as heroin became known.
"Noel Johnston single-handed wrecked Ballymena. He wasn't a street dealer. From day one, he was an importer," a former RUC drugs squad officer told us.
And despite being raised a Catholic he became best of friends with the town's growing army of loyalist drugs barons. Under Johnston's reign, the once-respectable Doury Road estate became a wasteland for heroin dealers as well as users.
It is understood Johnston was successful in a recent legal action to have seized property returned to him by the authorities.
But he was also said to have been devastated by the return of a cancer condition.
Only last year, father-of-two Johnston told friends he was penniless as a result of government attempts to close down his multimillion drugs empire.
He was forced to sell his luxury home last year and moved into a apartment block in High Street.
And despite being branded a 'Mr Big' by the RUC drugs squad, Johnston successfully avoided going to jail apart from a three-year sentence for possession of £250,000 worth of cannabis when he was caught after a high-speed car chase through Cullybackey village.
Unknown to him, Lady Diana was on a visit to Northern Ireland at the time and he mistakenly thought a helicopter was part of a drugs sting when it was in fact part of the royal security operation.
In a carefully planned action seven years ago, Assets Recovery Officers, aided by police, raided a warehouse behind Johnston's former home on the Ballymoney Road. Inside they discovered a huge 'boys toys' haul of vintage cars, vintage motor bikes and expensive paintings.
As recently as last year, Johnston was living in a luxury detached house on Greenmount Terrace. The property, which was built in 1776 - the same year as the American War of Independence - had been tastefully renovated.
Johnston - who had never been photographed before - was snapped by a Sunday World lensman as he stepped outside it.
Just over a year ago, Johnston put the property on the market and moved into social housing after his application for a Housing Executive home was turned down.
Johnston first came to public attention in the early 1990s when a drugs gang led by him were arrested by gardaí in Donegal.
A garda officer, working on his own, found Johnston and his mates exhausted and soaking wet on rocks near Malin Head.
Johnson - who acted as spokesman for the rest - claimed they had put out to sea in an inflatable rib boat, but experienced difficulties when a sudden squall blew up.
They were released without charge. But it later emerged that Johnston and the others were involved in a failed attempt to land £17 million of cannabis from the Pongeur Whisky cruiser.
Lucky to escape with their lives, Johnston and his pals struggled to get the rib back to the Donegal coast as the boat limped on to Kilrush Harbour in Co Clare where the massive drugs cargo was seized by gardaí.
It later emerged the drugs belonged to a millionaire dealer and Johnston had been operating as his right-hand man.
Johnston gained celebrity status in the Belfast drugs underworld when he won a marathon fist fight with Belfast drugs boss Paul Daly.
The pair met by chance in Tenerife where they were both living in the same apartment block along with their families.
One night, Johnston invited the Belfast man to visit his luxury apartment for sunset drinks on the balcony. And eye-witness told the Sunday World things were going well until - suddenly and without warning - Daly punched Johnston on the chin.
The strength of the blow set the Ballymena man's eyes spinning in his head. But he quickly recovered and set about battering muscle-bound Daly.
After 20 minutes of non-stop fighting, Daly admitted defeat and slinked back to his apartment with his tail between his legs.
In recent years, Johnston was in partnership with the former Ballymena UVF boss Paul Gray. They operated a bar together which has become a firm favourite with the immigrant community in Ballymena.
Last night, an underworld source in Ballymena said he expected Paul Gray to pack his bags in view of the increased police activity in the town.
The PSNI confirmed the Police Ombudsman had been called in to examine the circumstances surrounding Noel Johnston's sudden death.