The suit names as defendants Iowa Health System (UnityPoint), the parent company of the Illinois hospital that treated Prince days before his death in April 2016, Walgreens, North Memorial Health Care and Dr. Michael T. Schulenberg.

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Walgreens is named because the lawsuit alleges Prince received prescription medications from two Walgreens locations in Bloomington and Minnetonka in the days prior to his death. North Memorial is named because Schulenberg was an employee when Prince allegedly received health care services from him in the days leading up to his death.

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Among the lawyers questioning Johnson were those representing Dr. Howard Kornfeld, an addiction specialist who sent his son to Minnesota in an effort to meet with Prince just before his death, as well as those representing Schulenberg, North Memorial and Walgreens.

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"This was a traumatic event for my client," Johnson's attorney F. Clayton Tyler said following Wednesday's deposition. "He feels very sad over the loss of a good friend of his. To have to come back and go through this and re-litigate this whole matter has been very difficult."

An attorney representing Prince's next of kin declined to comment on the deposition, or on what's next in the case.

Editor's note: This story has been corrected to reflect that Dr. Howard Kornfeld sent his son to Minnesota in an effort to meet with Prince just before his death, and that he did not reach a civil settlement. Dr. Michael T. Schulenberg agreed to a $30,000 civil settlement with the U.S. Attorney's Office in April 2018 for violating the controlled substances act.