Liberia faced an excruciating choice on Thursday- deciding which handful of Ebola patients will receive an experimental drug that could prove either life-saving or life-threatening.

ZMapp, the untested Ebola drug, arrived in the West African country late Wednesday. Assistant Health Minister Tolbert Nyenswah said three or four people would begin getting it on Thursday. The government had previously said two doctors would receive the treatment, but it was unclear who else would.

These are the last known doses of ZMapp left in the world. The San Diego-based company that developed it has said it will take months to build up even a modest supply.

An Ebola outbreak that began in Guinea and spread to Liberia, Sierra Leone and Nigeria has killed more than 1,060 of the 1,970 people sickened since it was detected in March, according to the World Health Organization (WHO).