Body worn camera video showing a Texas Department of Public Safety (DPS) trooper used Signal to notify federal immigration authorities about an undocumented teenager last summer, prompted an agency-wide warning from a senior leader within DPS, email records show.

The 28-minute video from early May shows a quick hand-off: a trooper pulling over a high school senior who was on his way home from a night shift at an Austin fast food restaurant; the trooper sending federal immigration authorities a picture of the teen's ID through encrypted messaging application Signal; U.S. Immigration and Customs officials responding "detain" in the Signal chat before showing up and taking the teen into custody.

Within five days of NBC Austin affiliate KXAN publishing the footage, DPS' Deputy Director of Law Enforcement Operation sent chiefs an email saying, "it seems we are still experiencing issues with third-party messaging apps." Records show it was not the first time he raised concerns about apps, like Signal - that is known for allowing users to automatically delete messages, and issues properly preserving evidence, like conversations between law enforcement officials.