Police in India have identified four of six alleged attackers in the rape of a nun through CCTV footage, AFP reported. The assault occurred late Friday during the robbery of a convent and Christian school in the state of West Bengal.

Investigators are offering a $1,500 reward for leads in the case, AFP reported, and they have detained eight people for questioning.

The attackers stole several thousand dollars in cash, CNN reported, and assaulted the elderly nun, who remained hospitalized Sunday, when she tried to signal alarm.

In the course of the burglary, two other nuns and a building security guard were tied to chairs, Archbishop of Calcutta Thomas d’Souza told the BBC. The assailants also “vandalized the chapel, broke open the tabernacle and took away the ciborium, the sacred vessel used during mass,” the BBC reported.

The nature of the attack is unprecedented in India, d’Souza told AFP: “They not only committed a heinous crime, but they also vandalized the chapel. … This is the first time such an attack has happened in India.”

Christians comprise a 2.3 percent minority among India's predominantly Hindu population. In recent months, a string of attacks on churches in India, coupled with the rise of so-called forced "conversions" of religious minorities to Hinduism, have sparked public outcry and criticism of Prime Minister Narendra Modi. 

Federal police are leading the investigation at a time when sexual violence against women in India has drawn intense scrutiny. Earlier this month, the Indian government banned a British documentary, “India’s Daughter,” on the 2012 gang rape and murder of Jyoti Singh. Reports of rape and molestation in Delhi are on track to double this year, the Times of India recently reported.

Across India Sunday, Christian leaders held prayers for the nun, who is reported in stable condition, and were making plans for a candlelight vigil to be held Monday.