Mr Falsey, who was shot dead in his Cork home, had a bullet mailed to his house just weeks earlier.
It is thought a hitman from Dublin was recruited to kill him because of a drugs debt owed to a major Cork crime boss.
Mr Falsey died after being shot three times -- twice in the torso and once in the head -- at his rented home in Ashbourne Court, Carrigaline, Co Cork.
The father-of-two had not stepped up his personal security, despite the bullet threat.
Detectives believe his shooting was a professional killing, given that a semi-automatic gun was used, possibly equipped with a silencer.
Mr Falsey was associated with a drugs gang on Cork's southside and gardai are probing reports that he owed money -- possibly as much as €80,000 -- to the gangland figure.
Now, gardai have learned that two other Cork-based men, both with links to the drug trade, have received bullets in the post.
Both have refused to make formal complaints about the matter, and declined to supply further details to gardai. One case is understood to be related to a personal matter and is not linked with any gangland issue.
However, the other man is believed to have fallen foul of the same Cork drugs gang that Mr Falsey was associated with and has now fled his home.
"There are a lot of very scared people out there at the moment," a garda source said.
Over €30,000 in cash was recovered by detectives from a fridge in a lock-up in Riverstick where Mr Falsey used to keep his dogs.
Gardai stressed that, despite their interest in any debts Mr Falsey may have had, they are not ruling anything out, including the possible involvement of dissident republicans.