Paul Massey — known as "Mr Big" — was shot dead in Salford, near Manchester, in 2015 while John Kinsella, an enforcer who once intervened to rescue England footballer Steven Gerrard from a gangster's threat, was gunned down earlier this month near Liverpool.
A 37-year-old man was arrested at Manchester airport on Wednesday, May 30, in connected with the murders of Massey, 55, and Kinsella, 53.
Greater Manchester Police said a 48-year-old was also being held on suspicion of conspiracy to murder Massey and a woman, aged 39, was being questioned about assisting an offender over the Kinsella murder.
Shot Dead As He Walked Dogs
Kinsella was shot on May 5 in front of his girlfriend as they walked their dogs on a woodland track near a motorway sliproad close to the M62.
His girlfriend survived despite the gunman shooting at her. He then escaped on a bicycle.
Massey was killed in a machine gun attack outside his home in July 2015. He had led a Salford-based street gang called The A Team since the 1990s but the split into two factions.
A few days after his death a seven-year-old boy was shot in the leg in Manchester as the factional fighting threatened to get out of hand. There were also fears in the summer of 2015 that the feud might spread to Marbella in Spain.
Dawn Raids In Manchester
Greater Manchester Police carried out dawn raids on Wednesday in Heywood, Rochdale and Salford in a joint operation with Merseyside Police.
Detective Chief Inspector Carl Jones, from Greater Manchester Police's Major Incident Team, said the two murders remained "separate investigations."
Earlier this month the Liverpool Echo claimed Kinsella and Massey had been close friends and had gone on holiday together to north Wales shortly before the Mancunian died. Kinsella was a pall bearer at Massey's funeral.
In 2008 a court heard Steven Gerrard's father approached Kinsella after the Liverpool and England midfielder was threatened by George Bromley junior, the son of a notorious Merseyside gangster.
Kinsella intervened on Gerrard's behalf and smoothed over matters with Bromley junior, the court heard.
It is thought Kinsella may have been killed because he was planning retribution against Massey's killers.