Mr Frederick, 26, got outside first as Mr Nolan, who turned 42 yesterday, sprinted through the hospital forcing his way through closed doors as the building went into lockdown.
"When I got outside the person was in a blue hatchback. Nick yelled at him to stop the car. The person was calling out for a doctor and seemed to be rather angry, but he stopped the car," Mr Nolan said.
"After he stopped Nick turned to me and said 'distract him Mike, keep him occupied'."
Mr Frederick discreetly retrieved the Bushmaster rifle from the gun safe in the boot as Mr Nolan distracted the man by yelling at him.
"Nick had grabbed the Bushmaster and came back. He challenged the man, yelled out that he was armed police and to comply with his instructions," Mr Nolan said.
"As Nick was covering the man, I raced to the patrol car where the Glock pistol was in the gun safe in the front passenger seat. I got the Glock ... went back to cover Nick."
Faced with two armed police yelling at him, the man gave up. As the officers handcuffed him, they heard the sirens of other patrol cars converging on the hospital.
Yesterday the officers said they did not think twice before running into the firing line and would do it again if needed.
Mr Nolan has been a police officer for 10 months and Mr Frederick for three years. For both, Sunday was the most intense job they had attended. But neither feared for his own safety during the drama.
"It happened so fast we didn't really have time to stop and think about it. As I ran down the hall I did think 'what are you doing Nick?' but I just wanted to get to him. I knew I had to get there and back him up," said Mr Nolan.
"My main priority was assisting Nick and also keeping this person contained, keeping sight of him and making sure no members of the public were hurt. At the time I didn't really have a chance to be scared."
Mr Frederick agreed.
"I didn't have a chance to be scared at the time. Now it's been a couple of days the 'what ifs' have started to creep in. It still hasn't really sunk in."
Seeing the damage to the police car later on was "sobering". The hole in the windscreen and the shattered passenger window were one thing - but the hole in the rear of the car, the shredded paint and the dozens of shotgun pellet dents conjured images of what would have happened if the shot had hit either of them.
The pair have been called heroes, their courage commended by the Police Commissioner.
"We just did what needed to be done really," said Mr Frederick. Mr Nolan added: "It's just part of the job."