After Lukas had told Oak to test his Frequency, he watched with a mix of fear and admiration as Oak slammed into the boar-like ghoul and grappled it from underneath its chest. Lukas couldn't see exactly what Oak was doing, but it wasn't long until he saw blood fall out of a newly created hole in the ghoul's chest.
The ghoul was completely motionless after Oak had used his Frequency. Its eyes twitched and dilated so fast and sporadically that it was akin to a spasm of the eye. Oak scrambled out from under it and ran up to him, unaware and unfazed by the strange behaviour of the ghoul.
Lukas had been paying close attention to how much time had passed, the moment Oak ran up to him would have been the only moment he could have sent himself back in time to warn Oak. He looked Oak up and down but saw nothing to tell him that Oak was unwell in some way.
