In three interviews with federal agents, Headley’s wife said that he was an active militant in the terrorist group Lashkar-i-Taiba, had trained extensively in its Pakistani camps, and had shopped for night vision goggles and other equipment, according to officials and sources close to the case. The wife, whom ProPublica is not identifying to protect her safety, also told agents that Headley had bragged of working as a paid U.S. informant while he trained with the terrorists in Pakistan, according to a person close to the case.

...“We can confirm there was a lead based on his wife’s tip,” said an official who requested anonymity because of pending legal cases. “We can’t get into details.”

I've reported several times on his prior record and the sweetheart deal he got when he became a DEA informant. What's never been answered is whether he was working for a U.S. agency when he went rogue. The Government weakly, through unidentified officials, denies it.

This part of the article is telling.

A federal court discharged him from probation in December 2001, well before the scheduled end date in 2004, court records show. Within two months he was training in Pakistan with Lashkar, which had just been designated a terrorist organization by the United States and Pakistan, documents say.

After the September 11 attacks, Gilani told associates that he planned to train with Lashkar as part of a secret mission for the U.S. government, the person close to the case said.

“The FBI and