Albert Barnes Commentary 2 Kings 15:10

"And Shallum the son of Jabesh conspired against him, and smote him before the people, and slew him, and reigned in his stead." — 2 Kings 15:10 (ASV)

Before the people - that is, openly and publicly. The Septuagint renders the original words as a proper name, Keblaam, and presents him as the actual assassin, but with little justification.