Robert Mueller, the former special counsel whose investigation into alleged Russian interference in the 2016 US election defined much of Donald Trump's first term in office, has died aged 81.


The cause of his death was not immediately clear. CBS News confirmed his passing.


With deep sadness, we are sharing the news that Bob passed away, his family stated. His family asks that their privacy be respected.


Mueller previously led the Federal Bureau of Investigation (FBI) from 2001 to 2013, taking the office just days before the September 11 terror attacks. He is credited with reshaping it into a modern counterterrorism agency.


Survived by his wife, Ann Cabell Standish, and their two daughters and three grandchildren, Mueller leaves behind a legacy marked by complexity and significant public service.


His special counsel inquiry scrutinized Donald Trump's 2016 campaign, which faced intense scrutiny and criticism, leading Trump to condemn the investigation as a witch hunt. Despite the politically charged atmosphere, Mueller's integrity and professionalism earned respect across the political spectrum.


Former presidents George W. Bush and Barack Obama paid tribute to him, underscoring his commitment to the rule of law and national security. Bush expressed deep sadness over Mueller's death, highlighting his role in leading the FBI after 9/11.


As one of the most scrutinized legal figures of recent history, Mueller's investigation yielded multiple indictments and plea deals but ultimately concluded without establishing direct collusion with Russia. However, it affirmed the integrity of the electoral process and the ongoing debates surrounding political accountability.


Mueller continues to be viewed as a figure of integrity, dedicated to public service and committed to upholding the law during some of the most turbulent political times in recent history.