Hogan, who jumped from the balcony after his children, survived the 50-foot plunge and was acquitted in Greece on mental grounds of killing his son, Liam. His daughter, Mia, 2, survived.
Sarah Davidson of Hull, England, who was staying at the same hotel, told a court in Bristol she had heard a "horrific" argument before Hogan and the children appeared on the balcony, The Telegraph reported. Davidson broke down in tears as she described the scene.
"I couldn't comprehend why he pushed them or didn't try and reach out for them. I just couldn't believe it," she said.
Hogan's ex-wife, Natasha Visser, asked for the British investigation after her husband was acquitted in January. The couple had gone to Crete to try for a reconciliation in their marriage.