Many Texans were jolted awake early Friday by a blue alert on their cellphones related to a man suspected of violence against a police officer in Hall County in the Texas Panhandle.

The statewide alerts — blue, yellow, silver and others — are intended to collect tips from the public to help catch criminals who kill or seriously injure local, state or federal law enforcement, or find missing people.

They are shared with everyone, but you can turn off notifications on your phone.

If you have emergency alerts turned on, the alarm will sound loudly even if your phone is set to Do Not Disturb. So if you really want your phone to stay silent, you’ll want to know how to turn emergency alerts on and off.

On iPhones, open Settings, select Notifications, and scroll down. You can turn “Amber Notifications” and “Emergency Alerts” on or off.

Android phone users may find the emergency alert settings in different places depending on the Android version.

Open Settings. Select Notifications or Apps & Notifications.

Tap Wireless Emergency Alerts or Advanced, then tap Emergency Alerts.

Toggle Amber, Major, and Extreme alerts on and off.

On older phones, you may need to dig a little deeper into the settings to find the right spot.