New Yorkers learn the hard way about new wireless alerts

Jonathan Sanger | NBC News

Around 4 a.m. on Wednesday morning, many New Yorkers were unceremoniously yanked from their dreams by the sounds of their phones blaring. A child was missing and in imminent danger, so an AMBER alert was issued, triggering the mass wake-up call.

"I literally thought the city was under attack,"

. "Scariest wake up ever." "All of NYC woken up by terrifying noise," . "Thought it was carbon monoxide alarm, was gripped by panic over how to save my cats." Some tweeted that they thought there was an alien attack, a nuclear bomb, and all sorts of other disasters.

In reality, a 7-month-old boy's mom had kidnapped him during a supervised visit at a foster case facility. He was found, safe and sound, by Wednesday afternoon.

Since Dec. 31, 2012, AMBER alerts have been part of the national Wireless Emergency Alert program, which is also known as the Commercial Mobile Alert Service. AT&T, Sprint, T-Mobile, Verizon and other U.S. carriers participate in the Wireless Emergency Alert program. This is the same system which sends you alerts of imminent threats, such as hurricanes, earthquakes, tornadoes, evacuation orders, and more. It can also be used for alerts sent by the president of the United States, or his or her designee.

AMBER alerts issued through this system are up to 90 characters long and include basic information which indicates that an AMBER alert has indeed been issued for the area you're in and may include a license plate or other details about any vehicles which may have been used in an abduction. The alerts look a lot like text messages, though they do not incur any charges or count against any text message quotas you may have on your wireless plan.

Additionally, unlike text messages, these alerts are location-aware. They are sent using a technology which ensures that they are delivered immediately to individuals in a specific area. (This means that you could be a Floridian with a California cellphone number and visiting New York City, but still receive a relevant alert.)

In order for an AMBER alert to be issued, it should meet guidelines set by individual states. Those may include having law enforcement confirm that an abduction has taken place, that a child is at risk of serious injury or death, that there is sufficient information about the child or abductor, and that the child is 17 years old or younger.

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It's important that AMBER alerts are sent out as soon as the relevant criteria is met because, an information page put together by the Cellular Telecommunications & Internet Association (CTIA) explains, "statistics show that the first three hours after an abduction are the most critical in recovery efforts, and being able to quickly engage the public in the search for an abducted child can help law enforcement bring that child home safely."

This means that we sometimes get woken up in the wee hours of the night.

Of course, it is possible to opt out of Wireless Emergency Alert messages (save for the presidential ones). The process to do so varies based on device and carrier. If you don't want any more rude awakenings like the one you may have received, check your phone's settings.

—Rosa Golijan, NBC News