Duke got a ping on his phone about Andi's death so he realised that it was Miles who killed her at that moment. He tried to blackmail Miles, so he killed him.
Duke saw the news of Andy's death during the party at the lounge and blackmailed Miles to get his news program off the ground that's when Miles decided to kill Duke off by handing him the Pineapple filled drink.
Duke found out Andi was dead and clicked it was Miles who killed her. Showed Miles and essentially blackmailed him to give him a show on Alpha News. Miles, not wanting anyone else to know, saw the opportunity to kill him, and did it there.
BANDlCOOT t1_j2866ey wrote
Duke got a ping on his phone about Andi's death so he realised that it was Miles who killed her at that moment. He tried to blackmail Miles, so he killed him.