In an emergency, you can press the Power button quickly five times or more to start a blaring sound and automatically call emergency responders. If you sign in to your Google account, you can set your phone to send SOS text messages with your current location to emergency contacts and to record emergency video.
Adjust settings:


To change the default regional emergency number dialed for help, touch Call emergency services > Number to call for help, enter the number, and touch OK.
Press the Power button five times or more to start the countdown alarm and call for help.
Go to Settings > Safety & emergency > Emergency SOS, then turn Call emergency services off 
You can set up emergency information for first responders or others to view from your lock screen, such as your emergency contact and medical information (blood type, allergies).
Anyone who needs to view your information should:
From the lock screen:
To add your name or a short message to your lock screen for anyone who finds your phone:
If Android Emergency Location Service (ELS) works in your country and on your carrier's network and if you haven't turned off ELS, when you call or text an emergency number, ELS sends your location to authorized emergency responders to help them locate you.
If ELS is off, your carrier might still send the phone’s location during an emergency call. For more information, check with your carrier.
To turn ELS on or off:


To learn more about ELS, read Google's help.
Your phone can receive free alerts to inform you of public safety messages, threats to life and property (like extreme weather), and other emergencies.
When an emergency alert is sent out, 
You can turn most alerts off or on and adjust alert notification settings. Presidential alerts cannot be turned off.