From the canon sectionof Wookiepedia,
"He reluctantly pledged himself to service under his new Sith Master, Darth Sidious, who named him "Darth Vader," a title that he did not bestow lightly. Sidious then declared all Jedi enemies of the Republic and ordered Vader to kill the Jedi at the Temple, while he executed Order 66, during which clone troopers turned on their Jedi Generals and executed them on the spot. Leading the attack, Vader and the 501st Legion carried out this order. During the assault, Vader entered the council chamber and found a group of younglings trying to hide. Thinking Vader was still a Jedi Knight, one boy asked him what they should do, but the new Sith Lord slaughtered the boy and the other younglings. Also during the battle, Vader killed Jedi Masters such as Cin Drallig, before meeting with Sidious, who then sent him to Mustafar."
Source: https://starwars.fandom.com/wiki/Anakin_Skywalker#Fall_to_the_dark_side