1 Kings 2:8-9

2:8 “Note well, you still have to contend with Shimei son of Gera, the Benjaminite from Bahurim, who tried to call down upon me a horrible judgment when I went to Mahanaim. He came down and met me at the Jordan, and I solemnly promised him by the Lord, ‘I will not strike you down with the sword.’ 2:9 But now don’t treat him as if he were innocent. You are a wise man and you know how to handle him; make sure he has a bloody death.”

1 Kings 2:37

2:37 If you ever do leave and cross the Kidron Valley, know for sure that you will certainly die! You will be responsible for your own death.”

1 Kings 2:46

2:46 The king then gave the order to Benaiah son of Jehoiada who went and executed Shimei.

So Solomon took firm control of the kingdom.