Hello. Well, the situation raised by you is really very alarming. If we go by your descripttion of the building and sense of urgency in vacating the premises, it is not only a moral obligation, but also a duty of all the residents to vacate the premises as soon as possible.
The first thing you can do is to approach the Municipal Corporation, or the District Development Authority, which is empowered to inspect the condition of the building and issue a certificate as to the fitness of the building. If, upon proper inspection, it is found that the building is actually at a risk, then it can issue a notice mandating evacuating the building to demolish and reconstruct it.
If even then the recalcitrant member does not give his consent, you can approach the district court, or the magistrate to pass an order to forcefully evict the member. If the member contests the order, the matter will reach a higher court, but considering the circumstances, it is highly unlikely that any authority would allow the member to stay in such a building when by doing so, he is endangering the lives of all the remaining residents.
Hope this satisfies your query.