Federal prosecutors charged Nasir Ahmad Tawhedi with planning the attack in support of ISIS. He was arrested Monday in Oklahoma City. According to court records, he made his initial appearance in federal court Tuesday, but did not enter a plea. He remains in custody.

It isn't yet known whether the man, who worked for the CIA in Afghanistan, radicalized before or after he arrived in the U.S. following the chaotic American withdrawal.

An Afghan national living in OKC was charged with conspiring to conduct a terrorist attack. Here's what we know about the investigation so far.