Saif al-Islam Gaddafi, the son of former Libyan leader Colonel Muammar Gaddafi, has reportedly been shot dead, his political party confirmed on Tuesday, according to Libyan news agencies.

A lawyer representing the family told AFP that a “four-man commando” carried out the attack in Saif al-Islam’s hometown of Zintan, though it is not yet clear who was responsible. His sister, speaking on Libyan television, said he died near the border with Algeria.

Saif al-Islam, 53, was once considered his father’s heir and the most influential figure after Colonel Gaddafi. During his father’s rule, he played a key role in efforts to improve Libya’s relations with the West.

Colonel Muammar Gaddafi ruled Libya from 1969 until he was killed in a popular uprising in 2011. Following his father’s fall from power, Saif al-Islam and his siblings faced accusations related to actions during the Gaddafi era and were held by a militia in Zintan for six years.