It didn't take time for Rasmus to learn what happened in the woods. When Kevin was released by Ruby, he disappeared from there and appeared back in Oz.
Kevin was badly harmed by the girl and he could feel his body lose its strength. Appearing in front of Rasmus's chamber he asked the guard to inform him about his emergency visit.
When the guard returned allowing him to step in, he rushed like a scared person and dropped on his knees in front of Rasmus.
"Betrayal..." he said and held on to Rasmus hand showing him what happened in the woods before passing out.
Rasmus was never infuriated but now he wanted to ask his son where did he lack in his upbringing so he decided to go against his words.
Rasmus had already guessed there was something off in Coal's behavior but he never expected this to happen. From the day he was born he was told about his betrothal and it was to be married off to the queen of Oz.