Witnesses Saw Mel Gibson Hit Oksana Grigorieva

Did Mel Gibson attack Oksana Grigorieva physically?
The actor and his attorneys have not said a word about the infamous tapes, which makes sense. It's pretty clearly him on the phone, and there's no explaining away remarks such as "You should just say you're sorry and BLOW ME!!!!!!"
But he's adamantly denied any violence, and his fans have accused Oksana of being a gold-digging liar. Might there be witnesses who saw it, however?
According to TMZ, sources connected to Oksana Grigorieva say "third party witnesses" will tell L.A. County Sheriff's investigators they saw Mel Gibson punch her in the face January 6 during a heated altercation at her home.
This is the same alleged fight that they appear to reference in some of the tapes, and that she Oksana emailed her attorney about just hours after.
The Mel Gibson tapes are all from February 18.
An Oksana and Mel Pic
Is Mel Gibson's benefit of the doubt evaporating?
Witnesses have not yet spoken to Sheriff's investigators probing the domestic abuse allegations against Mel, but they will supposedly come forward soon.
Sources say at least one witness is someone who works with Oksana on her music, which Mel claims is pretty average in one of his voicemail rants.
At least one of the third party witnesses reportedly saw the star pull a gun on Oksana during the same altercation, after he allegedly punched her.
We're told Oksana's 12-year old son Alexander, who Mel is also accused of assaulting, has already spoken with Sheriff's investigators in the case.
Sources say during the mediation in May, Oksana said Alexander, whose father is Timothy Dalton, was hiding under the bed during the argument.
Concurrently, Grigorieva is being investigated for extortion of Gibson, and both are battling for custody of their eight-month-old daughter Lucia.