I HAVE A QUESTION ABOUT MY THRIFT PLAN SAVINGS PAYOUT AFTER RETIREMENT

I LIVE IN PA, AND PA IS AN EARNED INCOME STATE. I HAD A WITHDRAWAL 0F 153766 DOLLARS FROM MY TSP AFTER I RETIRED, AND TURBO TAX IS TELLING ME I OWE A STATE TAX OF 4804 DOLLARS. THE TAX WAS PAID ON THIS MONEY WHEN IT WAS EARNED. WHY AM I BEING DOUBLED TAXED ?