What is that horrifying alert that came out of your phone?

When authorities extended an Amber Alert Wednesday for a missing California teen believed kidnapped, it set off blaring alarms on thousands of mobile phones in Washington state, startling many who had no idea what was going on. And while many received the emergency messages several times Wednesday and Thursday, others were left wondering why they didn’t get the alert.

A massive manhunt continues for James DiMaggio, 40, who is believed to have killed the mother of Hannah Anderson, 16, and possibly her brother Ethan, 8. Authorities sent the Amber Alert in Washington because they believe DiMaggio and at least the teen girl could be heading for Canada.

The alert prompted plenty of complaints, with many people taking to social media to criticize the unexpected high-pitched squeal coming from their phones.

“I’m sorry, I don’t like this Amber Alert system,” says KIRO Radio’s Dori Monson. “It’s very startling.”

Monson says a number of listeners contacted him to complain, saying they were shaken by the shrill alarm, scaring them and forcing them to fumble for their phones while they drove.

The text alerts are part of FEMA’s new Wireless Emergency Alert program, which sends automatic messages ranging from Amber Alerts to emergency weather notifications.

The program has been in use since the beginning of 2013, and is credited with helping locate a number of abducted children, including one in Washington.

“We used it for the first time in April and in that case, the child was recovered,” says Sgt. Jason Hicks with the Washington State Patrol

But that alert first went out in the middle of the night, drawing the ire of thousands woken up by the shrill alarm. Hicks says the state subsequently changed its policies to prohibit the alerts between 10 p.m. and 7 a.m. However, a number of people report they got Amber Alerts on their phones early Thursday morning.

“Our producer got woken up around midnight, and mine went off at around 2 a.m.,” says KIRO Radio’s Linda Thomas. She admits she’s since turned the alerts off, an option provided by phone carriers.

Hicks says the state will look into why the most recent alerts went out overnight.

“We’re trying to make it basically as convenient as we can,” Hicks says. “We don’t want to wake people up in the middle of the night, that kind of thing, because we don’t want people to opt out. It’s a valuable resource.”

That resource is now provided by carriers representing about 98 percent of all U.S. wireless subscribers, according to the CTIA, the wireless industry trade association. But even though the program supports more than 200 models of phones, older phones, including the iPhone 4, do not receive them.

With the manhunt continuing, Hicks implores people not to turn off their alerts.

“The whole purpose of the Amber Alert is to have more eyes out there,” he says. “So if you opt out of it, it’s kind of defeating our purpose to have it to begin with.”