"if it's roll over to pension, the its beccome taxable events."

Your taxpayer cannot "roll over to pension" because a pension is an employer-controlled plan. That's why they might be able to roll to an IRA = under the individual's control.

"is it taxable or nontaxable?"

Did you ask your taxpayer what happened to the funds?

"but why withholding federal tax and state tax"

That's typically mandatory if your taxpayer had control of the funds; that's what "distribution" means.