Adam Clarke on 1 Kings 16:15

The people were encamped against Gibbethon - It appears that, at this time, the Israelites had war with the Philistines, and were now besieging Gibbethon, one of their cities. This army, hearing that Zimri had rebelled and killed Elah, made Omri, their general, king, who immediately raised the siege of Gibbethon, and went to attack Zimri in the royal city of Tirzah; who, finding his affairs desperate, chose rather to consume himself in his palace than to fall into the hands of his enemies.