The son of a Hawaii doctor testified against him, saying his father confessed to trying to kill his stepmother.

Gerhardt Konig has been charged with second-degree attempted murder. The anesthesiologist is accused of beating his wife, Arielle Konig, with a rock on the Pali Puka Trail on Oahu on March 24, 2025. He has pleaded not guilty.

Emile Konig took the stand Tuesday, saying minutes after the alleged attack, his father called him and confessed.

“What did the defendant tell you during that call, as close to word for word as you can remember?” Prosecutor Joel Garner said.

“That he would not be making it back to Maui and to take good care of the younger kids and that he had – that Ari, my stepmom, had been cheating on him and that he tried to kill her,” Emile Konig responded.

Prosecutors allege Dr. Konig first tried pushing his wife Arielle off a Hawaiian cliffside, and attempted injecting her with a syringe, before repeatedly smashing her head with a jagged rock.

“I asked what was on his shirt, ’cause it looked like I saw splatters of something on his shirt, and he said, oh it’s just her, meaning Ari’s, blood,” Emile Konig testified.

A pair of hikers say they found the couple- with Arielle covered in blood.

An hour later – Emile received another video call from his father- who in court Emile only referred to as “the defendant.”

“He asked me if I had told anybody and I said yes and I told him who I had told, and then – he said that he was just gonna jump and said that a couple times,” Emile Konig said.

He said the second call ended with his father saying: “I’m gonna go before the police catch me.”

Dr. Konig’s defense team says Arielle attacked him first after he confronted her about an emotional affair- and they say he hit her with the rock in self-defense.

During Emile’s cross examination, they pointed out there were some parts of the calls that he couldn’t remember.

Prosecutor Joel Garner then asked: “is there any doubt in your mind about the defendant telling you he tried to kill Ariel?”

Emile Konig responded: “no.”

The big question now is whether Dr. Konig will take the stand in his own defense.

ABC News contributed to this report.