While these things are going on in Judæa, a certain young man educated at Rhodes, by name Alexander, gave himself out as being the son of Antiochus (which was false), and assisted by the power of Ptolemy, king of Alexandria, came into Syria with an army. He conquered Demetrius in war, and slew him after he had reigned twelve years. This Alexander before he made war against Demetrius, had formed an alliance with Jonathan, and had presented him with a purple robe and royal ensigns.
For this reason Jonathan had assisted him with auxiliary forces; and on the defeat of Demetrius, had been the very first to meet him with congratulations. Nor did Alexander afterwards violate the faith which he had pledged. Accordingly, in the five years during which he held the chief power, the affairs of the Jews were peaceful. In these circumstances, Demetrius, the son of Demetrius, who, after the death of his father, had betaken himself to Crete, at the instigation of Lasthenes, general of the Cretans, tried by war to recover the kingdom of his, father, but finding his power unequal to the task, he implored Ptolemy Philometor, king of Egypt, the father-in-law of Alexander, but who was then on bad terms with his son-in-law, to give him assistance.
But he, induced not so much by the entreaties of the suppliant as by the hope of seizing Syria, joined his forces with those of Demetrius, and gives him his daughter, who had been married to Alexander. Against these two Alexander fought a pitched battle. Ptolemy fell in the fight, but Alexander was defeated; and he was soon afterwards slain, after he had reigned five, or as I find it stated in many authors, nine years.
Source: Sacred History (New Advent)