Matthew Perry paid his assistant $150k a year. He helped him overdose on ketamine
On the day of Perry's death, Iwamasa gave police a list of all the medications Perry was taking, but he left off ketamine and said nothing about the injections

Source: The Independent
On the day of Perry's death, Iwamasa gave police a list of all the medications Perry was taking, but he left off ketamine and said nothing about the injections