“Die.” As Aureolus Izzard speak, time seemed to stop.

[...]

Assassinated, strangled, poisoned, shot, beheaded, slaughtered, hacked, beaten up, burned, nipped, crushed, ganged up, frozen, drowned. No one knew with what method Himegami was to die.
With no wounds, no bleeding and no illness, she simply died.
Like a consumed battery, she was expended. If souls existed, hers was extracted from her flesh, leaving behind an empty shell.

Toaru Majutsu no Index vol.2 ch.3 pt.5