דברי הימים ב, פרק כ״ב, פסוק א׳

The residents of Jerusalem take the initiative to crown Ahaziah, the youngest son of Jehoram, as the new king of Judah. This decision is a step taken out of absolute necessity, as all of Jehoram's older sons had already been killed by a raiding band that previously attacked their camp.

Clarifying the origins of this deadly group, commentators note that these attackers came specifically from the Arab territories. This band of raiders had joined forces with the Philistine camp to wage war against Jehoram during the earlier conflicts [מצודת דוד, מצודת ציון, ביאור שטיינזלץ].