Celtic could face severe penalties from the football authorities after UEFA announced it had launched a disciplinary investigation.
As he crossed the goalmouth, McHendry stuck out his arm and made contact with the player.
The Brazilian goalkeeper briefly chased after the fan but then collapsed theatrically to the ground.
Glasgow Sheriff Court heard today that McHendry handed himself in to police the morning after the incident, telling officers he rushed down the stand and on to the pitch as the winning goal was scored.
He claimed he had got "carried away" by the late goal.
The court heard that the single father told police: "I was running over to celebrate with the team. As I was running by I tapped the keeper of AC Milan on the shoulder.
"I said 'Unlucky, Dida' and continued running towards the team."
McHendry, of Cambuslang, near Glasgow, will be sentenced next month after reports.