 According to lawmakers, agents knew that Thomas Matthew Crooks was on a roof nearby 20 minutes before he took his first shots. Lawmakers say the FBI has provided this timeline. Details from ABC's Andrea Fujii. At 5.10 p.m., Crooks is first identified as a person of interest, a full 62 minutes before the first shots. At 5.30, he's spotted with a range finder, which can be used to determine distances for target practice.