and the brain damage...

He could only stare vacantly at his fingers moving to pull the trigger.
A dry gunshot.
Before the sound reached his ears, it struck Accelerator right between the eyes with a
shock that felt like being walloped with a hammer. The impact to his head bent his entire
body backward. He heard an unpleasant noise from somewhere around his neck. His feet,
unable to withstand the blow, jolted up into the air.
But he still didn’t let go.
He would never let go.
“Error. Break_code_No000001_to_No357081. Administrative command canceled due
to improper usage. Reawakening serial number 20001 in accordance with descriptions.”
With a light, electronic sound, the final warning window vanished. As soon as he heard
the girl’s familiar voice, he understood.
He’d finished overwriting the dangerous code all by himself.
Strength left his hand. His body had been blown into the air by the bullet impact. Slowly,
slowly, he fell away from the warm girl.
Accelerator, now airborne, reached his hand out.
But his fingers couldn’t reach her anymore.
He’d wanted something, but none of that would be fulfilled.
He’d desperately picked something up, but it all fell from the palms of his hands.

(Damn, how naïve can I be? After all I’ve done—)
His vision quickly blurred and then went black. He slammed into the ground below as if
falling into the depths of hell. His muddy awareness crumbled, and his thoughts rapidly
tumbled into the darkness.
(—Did I really think saving somebody would give me a chance to do things over?)

- Toaru Majutsu no Index Volume 5, Chapter 3 Part 14