There is a video showing his arrest, a mile away from the school. How did he get a mile away from the school before being arrested? When arrested he was not wearing body armor, mask, helmet?
So he took an Uber wearing full battle gear to a school? Why has there been no interviews from The Uber driver regarding all this?
I think you may have answered your own question. Perhaps he ditched the body armor, etc., which allowed him to get a mile away from the school before he was arrested. They were looking for a perp in all black body armor, so a kid who wasn’t wearing this, could easily slip through.
He also didn't have his gun(s), backpack or duffel bag with him.
He ditched them in a 3rd floor stairwell and then blended in with the students exiting the scene.
He even had time in between to get a drink at a Subway outlet in the nearby Walmart.
He dropped all his gear and headed out with the other students fleeing.