Some residents weren't pleased, and it showed up on Twitter. After Keith Belajonas was found dead in Staten Island, N.Y., sports blogger Kyle Scott tweeted, "I really wish they hadn't found that guy from Drexel Hill dead, because I wanted to punch him in the face for that 4 AM Amber Alert."
"Had the same exact thoughts last night," tweeted Joshua Wojcik.
"That Amber Alert woke me out of my sleep," tweeted "Enigmatic Allure" of Philadelphia.
At the same time, the alert was interrupting TV and radio broadcasts and popping up on illuminated highway signs. Some such alerts even get printed on lottery tickets.
Robert Hoever is director of special programs at the National Center for Missing and Exploited Children, the Washington nonprofit that handles the secondary distribution of Amber Alerts. "Yes, it was pretty early," he said, "but the fact is, by 4 o'clock, there are already a lot of people on the road. Time was of the essence. When an Amber coordinator gets a request like this, it's a delicate balance between abuse or overuse of the system and the welfare of the child - and we always tip it in favor of the safety and welfare of the child. It was really the best possible tool we had."
To issue an Amber Alert, local officials contact state police in Harrisburg. Police must believe a child is in imminent danger of death or serious injury, said Trooper Adam Reed, a spokesman. Other factors also come into play: time since the child was last seen, descriptive information, and the reliability of witnesses.
For Thursday's alert, the state police Amber Alert coordinator went to work in the middle of the night to determine whether the situation met the criteria.
"We do have to be very selective before an Amber Alert is issued," Reed said. "We don't want a scenario similar to the Boy Who Cried Wolf to play out. So they are very selective with the circumstances, and fortunately, they're not warranted very often."
(This was the third Amber Alert this year in Pennsylvania, following six in 2013. New Jersey has had two this year, with one last year.)
Why cellphones? Since Jan. 1, 2013, Amber Alerts go out automatically through the Wireless Emergency Alerts (WEA) program, which includes millions of cellphone users. The system sends information directly to cellphones through nearby towers, taking into account the direction in which the abducted child may be moving. If you have a WEA-enabled phone, you automatically get three kinds of alerts: President, Imminent Threat, and Amber.
Enabled cellphones get the messages (usually a default feature) unless you turn the feature off, a different task for different phones. One type of alert can't be shut down: A presidential message in a national emergency.
That piercing tone? Many phones assign an arresting, attention-getting tone to the three classes of emergencies.
"Car identification is right next to direct photographic evidence in terms of importance," Hoever said. It was there in this case: gray Nissan Pathfinder, Pennsylvania tag JDH-7477, L.A. Kings decal in rear window. The system apparently worked superbly Thursday: Police credited a 911 call, from someone responding to the alert, for leading them to the suspect's car on Staten Island.
Hoever said that he hoped such awakenings continued to be rare, but that the multiplatform approach would continue: "If anything, we're trying to find more and more platforms. The whole concept is, the more eyes and ears searching for the child, the better your chances.
"We'd rather have people see the message repeatedly," he said, "than not see it at all."