Last week one of Brazil’s most courageous social leaders was brutally assassinated on the streets of Rio de Janeiro. Marielle Franco, a city councilwoman and human rights defender, was shot four times in the head by unknown assailants in a passing vehicle shortly after leaving a gathering of young black activists. Her driver, Anderson Pedro Gomes, was also killed (Report, 16 March).

Long before being elected to Rio’s city council in 2016, Marielle was widely known as a tireless and fearless advocate for the rights of Afro-Brazilians, LGBT people, women and low-income communities. A gay black woman born and raised in one of Rio’s poorest neighbourhoods, she campaigned relentlessly against spiralling police violence in the city’s favelas.

Marielle’s activism earned her many powerful enemies. She vehemently challenged the impunity surrounding extrajudicial killings of black youth by security forces and, two days before her death, had denounced the police’s role in the killing of a young black man named Matheus Melo. She was a leading critic of the military intervention in Rio de Janeiro and was the head of a city commission tasked with monitoring the intervention.

We are deeply concerned and shocked by this commando-style killing of a woman who was a voice for the voiceless and a symbol of resistance to state-perpetrated violence, militarisation and anti-democratic forces. Given that Marielle’s murder bears all the hallmarks of a targeted assassination, we call for the creation of an independent commission comprised of prominent and respected national and international human rights and legal experts and tasked with carrying out an independent investigation of the murder of Marielle Franco with the full cooperation of state judicial and police authorities.

Shortly before her death, Marielle asked: “How many others will have to die before this war will end?” We call for justice for Marielle Franco and the daughter and the partner she leaves behind, and for an end to the killings and criminalisation of activists, government opponents and low-income people in Brazil.

Ava DuVernay Film-maker

Rev Jesse Jackson Civil rights activist

Anielle Silva Sister of Marielle Franco

Chimamanda Ngozi Adichie Author

Arundhati Roy Author

Angela Davis Distinguished professor emerita, University of California, Santa Cruz

Janelle Monáe Singer and actress

Edward Snowden Whistleblower and president of the Freedom of Press Foundation

Shami Chakrabarti UK shadow attorney general

Naomi Campbell Model and activist

Ta-Nehisi Coates Author and journalist

Noam Chomsky Professor emeritus of linguistics at MIT, political theorist

Patrisse Cullors Co-founder of Black Lives Matter, LGBT activist

David Miranda First LGBT Rio city councillor, PSOL

Glenn Greenwald Journalist

Bertha Zúñiga Cáceres Daughter of the late Berta Cáceres, general coordinator of the Civic Council of Popular and Indigenous Organisations of Honduras (COPINH)

Wagner Moura Brazilian actor and director

Luciana Genro Founder of PSOL, former presidential candidate, Brazil

Marcelo Freixo Rio state representative, PSOL, Defence of Human Rights & Citizenship chair

Linda Sarsour National co-chair of the Women’s March on Washington, former executive director of the Arab American Association of New York

Ayo Obe President of Nigeria’s Civil Liberties Organisation

Baltasar Garzón International human rights lawyer

Thandie Newton Actress and activist

Celso Amorim Former Brazilian foreign minister

Danny Glover Actor, film director, and activist

Naomi Klein Author and journalist

Gael García Bernal Actor and director

Shaun King Journalist and civil rights activist

Pamela Anderson Actress and activist

Alfonso Cuarón Film-maker

Opal Tometi Co-Founder of Black Lives Matter, executive director at Black Alliance for Just Immigration

Oliver Stone Film-maker

Yanis Varoufakis Former Greek finance minister

Viggo Mortensen Actor

Renata Avila Guatemalan human rights lawyer

Owen Jones Journalist

Slavoj Žižek Philosopher, Birkbeck Institute for Humanities

Chris Williamson Labour MP