Zimri became king of Israel during the 27th year that Asa was king of Judah. Zimri ruled in Tirzah only seven days. This is what happened: The army of Israel was at Gibbethon, which was under Philistine control.
Baasha was the son of Ahijah. They were from the tribe of Issachar. Baasha made a plan to kill King Nadab. Nadab and all Israel were fighting against the Philistine town of Gibbethon. And that is where Baasha killed Nadab.