Task: Question Answering
Input (English): Passage: Police arrived at the embassy almost immediately after the first reports of gunfire, and, within ten minutes, seven DPG officers were on the scene. The officers moved to surround the embassy, but retreated when a gunman appeared at a window and threatened to open fire. Deputy Assistant Commissioner John Dellow arrived nearly 30 minutes later and took command of the operation. Dellow established a temporary headquarters in his car before moving it to the Royal School of Needlework further down Princes Gate and then to 24 Princes Gate, a nursery school. From his various command posts, Dellow coordinated the police response, including the deployment of D11, the Metropolitan Police's marksmen, and officers with specialist surveillance equipment. Police negotiators made contact with Oan via a field telephone passed through one of the embassy windows, and were assisted by a negotiator and a psychiatrist. At 15:15 Oan issued the DRFLA's first demand, the release of 91 Arabs held in prisons in Khūzestān, and threatened to blow up the embassy and the hostages if this were not done by noon on 1 May.Large numbers of journalists were on the scene quickly and were moved into a holding area to the west of the front of the embassy, while dozens of Iranian protesters also arrived near the embassy and remained there throughout the siege. Shortly after the beginning of the crisis, the British government's emergency committee COBR, was assembled. COBR is made up of ministers, civil servants and expert advisers, including representatives from the police and the armed forces. The meeting was chaired by William Whitelaw, the Home Secretary, as Margaret Thatcher, the Prime Minister, was unavailable.  The Iranian government  accused the British and American governments of sponsoring the attack as revenge for the ongoing siege of the US Embassy in Tehran. Given the lack of co-operation from Iran, Thatcher, kept apprised of the situation by Whitelaw, determined that British law would be applied to the embassy, despite the Vienna Convention, under which the embassy is considered Iranian soil.At 16:30, the gunmen released their first hostage, Frieda Mozaffarian. She had been unwell since the siege began, and Oan had asked for a doctor to be sent into the embassy to treat her, but the police refused. The other hostages deceived Oan into believing that Mozaffarian was pregnant, and Oan eventually released Mozaffarian after her condition deteriorated. 
Question: What is the last name of the person that released a hostage believing she was pregnant?
Output (English): Oan.