Ibrahim Mothana, a 24-year-old Yemeni activist, died Thursday.
Cause of death was not released.
Co-founder of the Watan Party and Arab Thought Foundation's 2011 ambassador, Mothana was known for his activism in Yemen and writings against U.S. drone policy.
The U.S. has been deeply criticized for its use of drone strikes in Yemen -- meant to target Al Qaeda militants -- due to a high number of civilian casualties.
Journalist Jeremy Scahill tweeted on Mothana's death:
Guardian columnist Glenn Greenwald added:
Last year, Mothana penned an op-ed in The New York Times, "How Drones Help Al Qaeda," arguing that "Drone strikes are causing more and more Yemenis to hate America and join radical militants; they are not driven by ideology but rather by a sense of revenge and despair."
This past May, Greenwald published Mothana's testimony for a Senate sub-committee when the activist was unable to attend the meeting.
Mothana wrote in the testimony: "We Yemenis got our first experience with targeted killings under the Obama administration on December 17, 2009, with a cruise missile strike in al-Majala, a hamlet in a remote area of southern Yemen. This attack killed 44 people including 21 women and 14 children, according to Yemeni and international rights groups including Amnesty International."
Mothana concluded, "I call on the United States to critically reflect on using targeted strikes and the existing counterterrorism policy in Yemen and to see that, it is insecurity and not security that these are creating in my country, the region, the US, and the entire world."