One of the most devastating moments in the five seasons of Breaking Bad is the murder of young Tómas, but the question of whether Gus Fring was responsible remains unanswered. On more than one occasion, a child is killed in Breaking Bad, but Tomás' murder is the one that remains a mystery to this day. The death of Tomás would set in motion a course of action in the Breaking Bad timeline that would eventually have violent results among the main players in the show, but the details of the killer have never been confirmed.
https://screenrant.com/did-gus-fring-kill-tomas-in-breaking-bad/