Dale Cregan lured unarmed police constables Fiona Bone, 32, and Nicola Hughes, 23, with a bogus emergency call before using a Glock handgun and a military grenade to kill them on September 18 last year.
Today, in a change to his plea at his trial at Preston Crown Court, 29-year-old Cregan admitted to the murders of father and son David and Mark Short.
The murder of David Short in August last year was done in a similar manner to that of the PCs, using the same gun and the same type of grenade.
In May, Cregan had gunned down Mark Short as he played pool in the Cotton Tree pub in Droylsden.
Cregan's barrister, Simon Csoka QC, began the day by asking six of the seven remaining counts to be put to his client.Cregan, wearing a grey Adidas top, then stood up and calmly answered "guilty" to murdering Mark Short and David Short.
He also pleaded guilty to the attempted murders of John Collins, Ryan Pridding and Michael Belcher, who were all in the Cotton Tree at the time on the evening of May 25 last year.
He also admitted causing an explosion at a property in Luke Road, Droylsden, on August 10, shortly after the murder of David Short.The jury foreman was then invited by trial judge Mr Justice Holroyde to formally return guilty verdicts on those counts.
The judge then told the jurors that the defendant remained on trial for the single allegation remaining against him - that he attempted to murder Sharon Hark at her home in Luke Road.