Mafia 107. Fever and Overdose

2. The Mafia used the father's ability. This option is viable if the Father is among the players who had immunity on the first night (otherwise, releasing the Father would be very unwise).

Why? The most ideal night kill on the first night doesn't leave clues, isn't interrupted, and isn't revealed. There's nothing you can do about it, and the chance of the Doctor healing him randomly is minimal. There's no point in using other kills.