Lo Scandalo - S3-E8
Question: How did Krieger manage to dispose of Savio's body and how did he even manage to get the entire bathroom cleaned up with so much blood in the room so quickly? With how much blood there was, it should have taken a long time to clean up.
Answer: It's called lying. He was an egotistical mad scientist, who was paranoid and obsessed with proving his work valid. He was willing to do anything to achieve his goals.
David wasn't exactly lying. He attempted to kill Bruce when he was still a child but ended up killing Edith instead when she tried to stop him. General Ross was even there when David was taken away so there is some truth to what David said to Betty.