Immediately afterwards, both the assassin’s hands disappeared.

They had not been severed.

Instead, everything beyond his two wrists had been turned into a single golden faucet. This put him in a similar situation to having his hands cuffed and the components making it up were nothing more than his normal arms and a normal faucet

[...]

Without hesitation, she turned on the faucet.

With the sound of flowing liquid, the dark red liquid that gave him life easily poured out.

Toaru Majutsu no Index New Testament vol.4 main.11