It all happened so fast.
One second Juston was struggling to free himself from Giant-Man's grip, yelling and shoving with all his strength against the enormous hand that held his legs bound while the Phoenix-powered Emma Frost descended upon his Sentinel with glowing eyes and fire in her hands.
The next minute, Juston's classmates had rallied. Out of the corner of his eye he saw X-23 landing gracefully from the air to the torn earth, with Emma Frost's blood on her claws, but his mind was already miles ahead. He ran to his hulking robotic friend at a sprint so he could frantically assess the damage the Sentinel had taken, climbed atop the splintered metal chassis to reassure himself that his best friend was still alive, at least for a few moments more.
There was no thought to what followed: at that point Juston was running purely on instinct and emotion. He yelled for the Sentinel to open the cockpit so he could clamber on inside, his thoughts racing at lightning-speed to diagnose what repairs needed the most attention in the least amount of time, if the robot was to survive another blast from Emma. There was no room in Juston's mind for doubt or thoughts of creeping futility.
Later on, for the life of him Juston would never remember whose idea it had been to charge Frost prematurely, his or the Sentinel's. All he could remember from the moments before was a gutted sense of horror, watching as the impossibly powerful mutant held his classmates suspended in midair with telekinesis using only the barest turn of her outstretched hand.
Then, he and the Sentinel were flying at her in a rage, energy-blasters set to fire—and only when Emma raised both hands above her head and exploded the world into yellow heat around them did Juston realize he was sentencing himself to death.
By then, it didn't matter. In a way it was almost a relief, because he knew his Sentinel would have done the same for him. He knew it even as the metal of the cockpit folded in around him under the force of the blast, crushing his body inside. Acceptance gave way to mindless panic when the pressure increased, however, and seconds later screams upon screams of pain were tearing themselves from his throat, struggling to make himself black out if only to escape the agony of his skeleton ripping apart.
Somehow, in the midst of it all, Juston had an epiphany that the pain meant he hadn't died quickly, or mercifully. He was suffering still because his Sentinel had done its best to implode in such a way that Juston wouldn't be killed in the cockpit for as long as possible, preserving the last pockets of space by inches around the hull. In Juston's agony, he had a hard time mustering any gratitude for this act of terrible salvation on the part of the machine, but he did his best to try anyway. Preserving those last few precious seconds of Juston's life couldn't have been easy.
Then, all thoughts flew from Juston's mind when the remaining oxygen was ripped forcibly from his lungs by another tearing impact. The stifling darkness of metal that was crushing him within the Sentinel's cage of a body evaporated, transforming into searing fire and whiteness, and a pain like ripping knives all over that would surely end in his death.