The grandfather of an American teenager who was killed in a drone strike in Yemen said he plans to petition a federal court Friday, saying the Obama administration "must answer for its actions and be held accountable."

Nasser al-Awlaki, father of high profile al Qaeda leader Anwar al-Awlaki and grandfather to Anwar's son Abdulrahman al-Awlaki, made the announcement in an Op-Ed in The New York Times today.

Abdulrahman was 16 years old when he was killed in a strike in Yemen in the fall of 2011 just weeks after Anwar was killed in a separate strike. Altogether, American drones have killed at least four U.S. citizens since 2009, but Anwar was the only American purposefully targeted, according to Attorney General Eric Holder.

U.S. officials referred to Anwar al-Awlaki, who was known for long online videos in which he called for attacks on the U.S., as a "senior operational leader" of al Qaeda and he was linked to more than a dozen terror plots. However, as referenced in Nasser al-Awlaki's letter, the U.S. government never charged him with a crime.

Though President Obama spoke about the significance of Anwar al-Awlaki's death when he was killed in September 2011, the U.S. government has been less forthcoming about the strike that killed his Colorado-born teenage son in October of that year, only saying he was not the target.

"Nearly two years later, I still have no answers," Nasser al-Awlaki said in the Times. "The United States government has refused to explain why Abdulrahman was killed… My grandson was killed by his own government… Shouldn't it at least have to explain why?"

With the help of human rights groups, Nasser al-Awlaki has attempted legal action against the U.S. government before, but in two cases he said the courts dismissed his claims because the targeting killing program was outside their jurisdiction.

In February, the White House defended the program.

"We conduct those strikes because they are necessary to mitigate ongoing, actual threats, to stop plots, to prevent further attacks and, again, to save American lives," White House Press Secretary Jay Carney said then. "These strikes are legal, they are ethical, and they are wise."

The Center for Constitutional Rights and the American Civil Liberties Union filed suit against senior CIA and military officials last year over the American's killed. Oral arguments will begin in a federal court in that case Friday.