NBC News"Mysterious, middle-of-the-night drone flights by the U.S. Secret Service during the next several weeks over parts of Washington — usually off-limits as a strict no-fly zone — are part of secret government testing intended to find ways to interfere with rogue drones or knock them out of the sky, The Associated Press has learned. A U.S. official briefed on the plans said the Secret Service was testing drones for law enforcement or protection efforts and to look for ways, such as signal jamming, to thwart threats from civilian drones. The drones were being flown between 1 a.m. and 4 a.m.

Access the NBC news article and video, which includes an interview with Dr. Humphreys.