During the Delta 4 launch on the evening of August 7, 2013 I was able to capture 3-4 lights that formed a triangle formation that held formation while the Delta 4 released its boosters until the rocket went out of sight.
Note from The Black Vault: After seeing this video, I wanted to add what I believe is the explanation for these UFOs. Around that time during a Delta 4 launch, there are 4 solid booster engines that are jettisoned from the Delta 4 rocket. Although it's a cool video, I believe this is explainable and identified.
This case is archived here for reference and research. I also included a high-resolution video of a Delta 4 launch, which shows a close up of the engines being jettisoned.