Both Enright and McLoughlin have friends in the Dublin crime scene, with Cabra native Enright known to associate with Alan and Wayne Bradley, who are currently serving time for conspiracy to rob a cash-in-transit van.
McLoughlin, from Balbriggan, has convictions for assault and had a four-year sentence suspended for attacking a man in Ballymun and also assaulting a garda while being fingerprinted.
McLoughlin was also a pall-bearer at the funeral of one Dublin's most notorious gangsters, Eamon 'The Don' Dunne.
"What we are looking at here is two men who were both targeted within a day of each other.
"One was in his gym, and the other was near one he uses," said a garda source.
"While these men would not be well-known to each other they both swim in the same shark-infested waters and could have enemies in common," he added.
One line of inquiry common to both cases now is that the hits may have been ordered by the Real IRA group once led in Dublin by Alan Ryan, who was shot dead last September.
In an appeal for information on the shooting of Enright, gardai have asked for the public's assistance in tracing a silver Mini with a Northern registration plates that left the scene of the shooting at Ballyboggan Industrial Estate in the direction of Finglas.
But investigators have said that the Northern plates do not mean that they can take for granted a Northern link to the shooting.
"These plates could have been put on the car to throw gardai off the scent and send them in an obvious direction.
"The investigation is in its early stages and there is a lot of CCTV from premises and traffic cameras to go through yet," said the garda source.
Sean Enright was last night still in surgery for gunshot wounds to his upper body and neck as his family kept vigil at the Mater Hospital.
Gardai said the fact that both Enright and McLoughlin attended their gyms at virtually the same time every day meant their potential killers were able to establish a familiar pattern which made planning their executions easier.