Key witness in Mel Gibson assault case dies

A key witness in the Mel Gibson assault case has died.

The eyewitness - who was looking after the 'Braveheart' star's 10-month-old daughter Lucia when he allegedly attacked ex-girlfriend Oksana Grigorieva - had reportedly been battling cancer for some time and passed away at the weekend, RadarOnline.com reports.

The unnamed babysitter witnessed the actor's rage first hand when he reportedly flew off the handle about Oksana leaving the couple's daughter with the nanny to go and watch her 12-year-old son Alexander play in a basketball match.

According to a testimony by Oksana, the nanny fled to a bedroom with Lucia to escape the furore and could hear Mel ranting down the phone.

However, the woman never made a direct statement about the alleged incident to law enforcement officers, and left the star's mansion before Mel reportedly punched his ex-girlfriend in the face as she held their baby daughter.

The unnamed employee was said to be a target of the 54-year-old actor, who branded her a "wetback" and suggested he was going to report her to immigration authorities.

Mel was allegedly recorded telling Oksana: "I will fire (name omitted) if she's at your house. I will make it known and fire her. I'll report her to the f***ing people that take f ***ing money from the wetbacks, ok?"