Albert Barnes Commentary 1 Kings 16:11

"And it came to pass, when he began to reign, as soon as he sat on his throne, that he smote all the house of Baasha: he left him not a single man-child, neither of his kinsfolks, nor of his friends." — 1 Kings 16:11 (ASV)

Neither of his relatives, nor of his friends - Zimri’s measures were extraordinarily severe. Not only was the royal family exterminated, but the king's friends, his counselors, and his favorite officers were also put to death. Omri, who had been in the confidence of the late king, would naturally fear for himself and resolve to take the course that promised him at least a chance of safety.