Thomistic Predestination and Free Will

What is the role of free will in Thomistic predestination? My understanding of Thomist teachings: - people have free will to do what they want - everyone gets sufficient amount of grace (Sufficient for what, if they will go to hell as they live a sinful life.) - God just chooses some for salvation (predestines them), gives them a special amount of grace (efficacious grace) and these will go to Heaven - the others (who got sufficient amount of grace) are reprobates who go to hell I do not see any real connection between free will and grace - I suppose there is no. Thus, I do not understand how God chooses whom to provide efficacious grace and how this can be aligned with a loving God (e.g. what if he chooses killers etc. for salvation).