The agreement was revealed fewer than two hours before a scheduled news conference during which Carver County, MN officials are expected to announce what, if any, criminal charges will be brought in Prince's death, and against whom.
Metz added it was likely Prince had also taken one of the counterfeit Vicodin when he overdosed on a private jet the week before he died.
A laboratory report obtained by The Associated Press notes that one of the pills found in a prescription bottle with Johnson's name contained oxycodone.
In a separate development, a doctor who treated the musician in his final weeks has been fined for allegedly writing a prescription knowing it would be used by another person, the U.S. Attorney for Minnesota said in a statement.
He gave Johnson 15 percocets, Metz said, which were all "because Prince wanted to protect his privacy".
"[Johnson] continues to deny that he had anything to do with the death of his close friend, Prince", Tyler said in a statement.
In all, Metz said nobody associated with Prince - including Schulenberg, Johnson and the pop star himself - likely knew Prince was taking tainted medication. He turned to painkillers as a solution, which eventually led to his death from taking fentanyl, a synthetic opioid that is many times more powerful than heroin. Prince was pronounced dead at 10:07 a.m.
Schulenberg's attorney, Amy Conners, has disputed that and did so again Thursday, saying that Schulenberg settled the case to avoid the expense and uncertain outcome of litigation.
The day before Prince's death, his representatives also reached out to Howard Kornfeld, a Mill Valley doctor, addiction specialist and nationally recognized expert in treating opioid addiction.
Several videos released showed the interior of Paisley Park during the beginning of the police investigation, including footage of Prince laying lifeless outside of an elevator. That prescription was not linked to Prince's death.
Schulenberg is not now a target of any criminal investigation, federal prosecutors said in a letter to his attorney.
When Metz arrived at Paisley Park to deliver the results of the testing on April 21, emergency crews were already on site.
Investigators were told that the singer, whose legal name was Prince Rogers Nelson, had a history of going through withdrawals believed to be tied to prescription pain medication abuse, the unsealed documents showed.
Because the investigation has concluded, Metz said, case evidence such as crime scene photos will now be released.