At some stage in the night he and one of his friends had a fight about a woman.
Trying to resolve the situation he decided to ask the woman to leave.
But when he went to speak with her, Schmidt noticed she was talking to Mr Marshall.
He told the court that he went to Mr Marshall and told him to "f*** off", to which Mr Marshall replied something that Schmidt could not recall.
"I felt annoyed that he had responded to me like that," Schmidt said.
"I pushed him with my left hand to the front region of his chest/shoulder.
"It was not overly dramatic, but I could not say for sure how hard I pushed him."
He was in disbelief and could not comprehend what happened when Mr Marshall fell through the window, and did not intend for Mr Marshall to die, nor to hurt him, he said.
He left the hotel and saw Mr Marshall lying on the ground, but his instinct told him to home to go home and gather his thoughts.
He said he still could not comprehend what had happened.
The trial is due to finish this week.