AUSTIN (KXAN) — Twenty minutes after three people were killed in northwest Austin Sunday, the City of Austin said more than 26,000 people in the area received the first email or text alert telling them to shelter in place.

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Emergency shelter-in-place text alerts sent to people near the triple murder scene in NW Austin involving suspected shooter Stephen Broderick

911 dispatchers sent two more emergency messages over the next four and a half hours as law enforcement, SWAT units and helicopters searched for suspected shooter Stephen Broderick in a heavily-wooded area nearby.

A screenshot of the text messages people received are pictured to the right. The final one sent just after 4:30 p.m. said “it is now safe to go outside.”

Several people who live in the area told KXAN reporters who were on the scene that they never got the alerts.

Bryce Bencivengo, Communications Manager for the City of Austin’s Office of Homeland Security and Emergency Management, said that could mean those people have not registered with the Warn Central Texas program or updated their location information in the system.

It is a voluntary regional notification system (RNS) used by the Capital Area Council of Governments for the following the Central Texas counties: Bastrop, Blanco, Burnet, Caldwell, Fayette, Hays, Lee, Llano, Travis and Williamson.

The RNS program, run by Everbridge, allows local officials to contact people in their communities by cellphone, email, text or mobile app during times of disasters or public safety events. In order to receive the alerts, citizens must register specific addresses in the system, such as a home and work address. Users can add additional addresses like schools or daycares.

Bencivengo said CAPCOG and Everbridge do not share the personal information in the database with anyone else for any other reason. CAPCOG also aims to keep the messages very specific to emergencies that require action — including sheltering in place, boiling water during a boil water notice or evacuating due to a threat of flooding or a fire.

The system requires users to create a login, which means people can update phone numbers, email addresses and physical addresses if they change.

Click here to register or update your Warn Central Texas information.