When Elsworth Toohey and Peter Keating were arguing about Cortland and Toohey was trying to force Keating to admit that Howard Roark had designed the whole thing, they had the following exchange:
"It's worse... what you're doing... it's much worse.."
"Than what I did to Lucius Heyer."
"What did you do to Lucius Heyer?"
"I killed him."
"What are you talking about?"
"That's why it was better. Because I let him die."
"Why do you want to kill Howard?"
"I don't want to kill him. I want him in jail..."
Toohey never pressed for details on what he meant by that. What actually happened is that Peter went to Heyer's house to try to talk him into retiring so that he could be made a partner. Their argument caused Heyer so much stress that he ended up having another stroke and dying. Peter realized that, at some level, he had subconsciously wanted that to happen.
Why didn't Toohey press for details or do anything about that? Granted, under his sympathetic facade Toohey was an uncaring jerk who was just after power, but still... why did he just leave it at that? Was he being an uncaring jerk here, or did he think that Peter was just raving and not take his confession seriously?