This led him into direct confrontation with his former associates, members of one of Ireland's most dangerous drug gangs. The leader is a convicted killer who was closely linked to international drugs lord Brendan Kinlan.
Kinlan is in an English jail after police busted him with £1m worth of amphetamines.
O'Toole (32) was betrayed by close associates and his body was found dumped in a ravine in Trooperstown, Co Wicklow, yesterday.
The Herald first exposed the open threats on O'Toole's life in September 2011 when his father's house was shot at and graffiti was daubed on the walls of his local estate in Bray, Co Wicklow. Messages branding him a 'rat' were daubed around the estate where he grew up in Bray. 'We are waiting. Real IRA won't save you,' said one message. Others accused him of being a police informer.
It has also emerged that O'Toole was among the main suspects behind one of the biggest gun raids in years.
He was the brains behind the theft of 29 rifles and shotguns from a licensed gun shop in Ashford last September. However it has been established that O'Toole had a major row with those behind the robbery and had been fearing for his life since Christmas.
"It appears he was betrayed by someone he felt he could trust," said a source.
The raid on a gun shop took place six days after Alan Ryan was gunned down near his home on September 3 -- and just hours before his funeral.
Gardai had obtained intelligence in recent days that O'Toole had been shot dead, but snow hampered the search for his body. Officers scoured parts of Trooperstown last week -- but found his body after receiving "credible information".
The clearing of the snow finally led to his body being discovered.
O'Toole was lucky to escape when he was targeted in a feud-related shooting in Enniskerry, Co Wicklow, in 2011. He was shot in the stomach as he wrestled with the gunman.