Eusebius of Caesarea — on 2Tim 4:17 (ECCLESIASTICAL HISTORY 2.22)

“Story has it that the apostle, after defending himself, was again sent upon the ministry of preaching and coming a second time to the same city met death by martyrdom under Nero. While he was being held in prison, he composed the second epistle to Timothy, at the same time indicating that his first defense had taken place and that martyrdom was at hand.”