You took a $10,000 distribution from your IRA. That makes it taxable income to you. Any withdrawal from an IRA is taxable income. It doesn't matter what you did with the money after you took it out of your IRA.
I'm not sure what you mean by "the 10% tax underpayment." Do you mean the 10% penalty for an early withdrawal before you are 59 1/2 years old? That penalty doesn't apply to withdrawals from an inherited IRA.
