Sub to shoot Technical Foul free throws

[BDevil15]

Hi Guys, obligatory I'm a coach not an official and I appreciate all that you guys do. I can not find my rulebook this morning so just want to come to the source. High School boys, player on opposing team receives a tech late in the game last night. I go to sub my best free throw shooter to shoot the free throws and official says I have to choose from someone who was on the floor at the time. It worked out great actually and one of my kids who rarely scores got to shoot them but am I just so tired that I'm totally wrong on this? Can't anyone on the bench or floor shoot those free throws?

Thanks for what you guys do and I apologize for myself and my fellow coaches, you guys do great things for kids.