A 21-year-old suspect allegedly planned an attack on police "similar to the 2016 Dallas ambush," the FBI's Houston office said.

Those messages include 19 images from the Dallas crime scene and of Micah Xavier Johnson. They also show three images Gregori reportedly took in secret while "stalking" local police officers.

In July 2016, 25-year-old Micah Xavier Johnson shot police ... some text messages included images from the Dallas crime scene and of Johnson, the affidavit states. Other messages Gregori allegedly ...