I wonder about dinosaur "rage". In terms of classification dinosaurs can probably be positioned somewhere between reptiles and birds, both taxonomy-wise and intellectually. No doubt some dinosaurs might react negatively to injury but "rage" might be beyond them. Picture the largest bird--the ostrich--shot and wounded. Have you ever heard of this dinosaur descendant charging his tormentor like a wounded leopard? Now a triceratops was no doubt capable of major self defense. It's horns were likely used against other male rivals but might also prove useful against large predators like T. rex. A T. rex attack might very well be attended by a very active self defense including full-blown charges, although such behaviors were probably completely instinctive.
T. rex and triceratops were similar sized beasts--both roughly the size of African elephants. On the face of it, it might seem impossible for T. rex to pull down a triceratops. After all, much of the front half of the body was covered by a boney frill and impressive horns. There was no neck to grab on to and given the T. rex anatomy, it might be tough for him to get down low enough to grab a leg. Therefore, T. rex would have been limited to slashing at the rear portion of no doubt a highly mobile and highly defensive triceratops. If triceratops, an animal that usually traveled in herds, put up a group defense, the T. rex problem would grow exponentially. Of course, T. rex may also have attacked in groups. Possible but our nearest T. rex descendants might be considered predatory birds like hawks and falcons. With the solitary exception of the Harris hawk, all are solitary hunters.
To bag a triceratops, the best bet would be a body shot with an adequate caliber and a well-constructed solid. A frontal brain shot would involve too much luck. You would have to be an excellent anatomist to center the tiny brain.