You self certify and no proof or police report is required. Note that the violence has to have occurred within the last 12 months. While the 10% penalty is waived you still have to pay your usual federal and, if applicable, your state income tax. But you can get the tax back if you repay the withdrawal within 3 years. The withdrawal amount is limited to the lesser of $10,000 or 50% of your vested amount in your plan.
