Det Ch Insp John Caldwell was shot several times in front of his teenage son in the car park of a sports complex in Omagh on 22 February.
He remains in hospital where he is in a critical condition but stable condition under sedation.
Six other men were previously arrested by detectives investigating the attack and they have also all been released unconditionally.
The two men released on Sunday night were aged 57 and 33.
Police have said they believe the shooting was carried out and claimed by dissident republican group the New IRA.
Detectives also believe loyalist criminals helped in scouting out DCI Caldwell’s movements and provided the two guns used in the murder bid.
The PSNI said two gunmen fired 10 shots at the officer as he was putting footballs into the boot of his car.
At least two other vehicles were hit by bullets, detectives said.
On Monday, police released CCTV footage of the car believed to be used by the gunmen.
It was then seen on the M1 driving towards the direction of Coalisland and Omagh the day before the shooting.
The car was later found burnt out on the Racolpa Road outside Omagh.
Crimestoppers has offered a £20,000 reward for information leading to the arrest and conviction of those behind the murder bid.