The timing differed from phone to phone but sometime between late Monday and early Tuesday many mobile phones across Southern California received an alert regarding James Lee DiMaggio, suspected of killing Christina Anderson, 44, and kidnapping one or both of her children, Hannah, 16, and Ethan, 8, the Los Angeles Times reported.
The alert described the vehicle DiMaggio was believed to be traveling in; authorities said they believe he may be attempting to flee to Canada.
Some cellphones received only a text message, others buzzed and beeped as part of the Wireless Emergency Alert program, a cellphone equivalent of the Emergency Alert System that creates a high-pitched test tone on television.
Cellphone owners will receive messages automatically based on their proximity to the emergency, not on their phone number, officials said.
"If you're from Texas and that's where your phone number is based and you're traveling in California at the time of the Amber Alert, you'll receive the text message about the Amber Alert in California on your Texas-based phone," California Highway Patrol spokeswoman Fran Clader said.
The system began Jan. 1 and requires cellphone customers to opt out if they wish to stop receiving alerts.
To opt out users must change their phone's message or alert message settings automatically included on phones capable of receiving alerts.