Blue Alerts are issued to help catch people who are believed to have wounded or killed local, state or federal law enforcement officers. Here are the criteria for a Blue Alert: A law enforcement officer must have been killed or seriously injured by an offender.

Benjamin Hanil Song is accused of shooting an Alvarado police officer during an attack on the Prairieland Detention Center.

Texas is one of several states that use Blue Alerts, but what is it, and how does it differ from AMBER Alerts?

Recordings provided to CBS News showed first responders asking for an emergency alert to be sent, but dispatchers delayed because they needed special authorization.

As devastating floodwaters swept through the Hill Country in the early hours of July 4, a volunteer firefighter requested a mass emergency alert to warn residents.

While there was resounding pushback over the state's historical use of the alert system, some users provided alternatives for those who wanted a way to stay informed when it comes to severe weather.

A Texas firefighter pleaded for an alert amid rising flood waters. It took an hour to go out - Leaked audio provides new alert timeline as officials face scrutiny over when residents first learned of

President Trump is visiting Texas to meet with first responders, local officials and families of some of the victims in the aftermath of the catastrophic flooding. NBC News Priscilla Thompson reports from Kerrville,