Choice is not intention - they are different… Intention stands in relation to choice as end to means. The intention comes first - then a choice is made in reference to it.
Alternate scenario - a grenade is thrown. I could jump on the grenade and save some lives - or everyone dies. Can I do it? Of course - in no way do I choose or intend any damage from the grenade to anyone, myself included. (This was a mistake that Grisez made - it was famous… and then, if I recall, you see some of this nonsense come up in the super-famous paper in The Thomist from him and Finnis and Boyle on craniotomy, defending their action theory, I think in the first issue in 2000).
De Lugo could be helpful, as would a closer reading of the Q 64 A 7 - and also Long’s Teleological Grammar of the Moral Act, specifically the first chapter. (There is a small problem in the first chapter which I think sets up later arguments for trouble, but I digress.)