The Events which happened at this Time to Dionysius and those in Egypt
24 He says farther on: The presbyters, Maximus, Dioscorus, Demetrius, and Lucius concealed themselves in the city, and visited the brethren secretly; for Faustinus and Aquila, who are more prominent in the world, are wandering in Egypt. But the deacons, Faustus, Eusebius, and Chæremon, have survived those who died in the pestilence. Eusebius is one whom God has strengthened and endowed from the first to fulfill energetically the ministrations for the imprisoned confessors, and to attend to the dangerous task of preparing for burial the bodies of the perfected and blessed martyrs.
25. For as I have said before, unto the present time the governor continues to put to death in a cruel manner those who are brought to trial. And he destroys some with tortures, and wastes others away with imprisonment and bonds; and he suffers no one to go near them, and investigates whether any one does so. Nevertheless God gives relief to the afflicted through the zeal and persistence of the brethren.
26. Thus far Dionysius. But it should be known that Eusebius, whom he calls a deacon, shortly afterward became bishop of the church of Laodicea in Syria; and Maximus, of whom he speaks as being then a presbyter, succeeded Dionysius himself as bishop of Alexandria. But the Faustus who was with him, and who at that time was distinguished for his confession, was preserved until the persecution in our day, when being very old and full of days, he closed his life by martyrdom, being beheaded. But such are the things which happened at that time to Dionysius.
Source: Church History (New Advent)