Read this and answer the question

On 27 June, the ICC issued arrest warrants for Gaddafi, his son Saif al-Islam, and his brother-in-law Abdullah Senussi, head of state security, for charges concerning crimes against humanity. Libyan officials rejected the ICC, claiming that it had "no legitimacy whatsoever" and highlighting that "all of its activities are directed at African leaders". That month, Amnesty International published their findings, in which they asserted that many of the accusations of mass human rights abuses made against Gaddafist forces lacked credible evidence, and were instead fabrications of the rebel forces which had been readily adopted by the western media. Amnesty International did however still accuse Gaddafi forces of numerous war crimes. On 15 July 2011, at a meeting in Istanbul, over 30 governments recognised the NTC as the legitimate government of Libya. Gaddafi responded to the announcement with a speech on Libyan national television, in which he called on supporters to "Trample on those recognitions, trample on them under your feet ... They are worthless".

What position was held by Gaddafi's brother-in-law?
head of state security