California residents were angered Monday night when the state’s first Amber Alert -- issued for two missing children, Hannah and Ethan Anderson, and their alleged kidnapper, James Lee DiMaggio -- woke them up with a loud alert sound in the middle of the night.

The message, which asked residents to look for a blue Nissan, was sent at different times between late Monday night and early Tuesday morning to the cell phones of residents of the state. According to the Los Angeles Times, a  Nissan Vera with California license plate 6WCU986 belongs to James Lee DiMaggio, who is suspected of killing 44-year-old Christina Anderson and reportedly kidnapping her children, 16-year-old Hannah and 8-year-old Ethan, in San Diego.

California Highway Patrol officials said Monday’s Amber Alert was the first time the state's general population was notified through their cell phones. You can read the full Amber Alert here.

Many residents in California complained about the 10-second-long loud screeching and buzzing in the middle of the night. According to the L.A. Times, the Amber Alert's actual sound differed from phone to phone: Some phones buzzed and beeped repeatedly, some got multiple alerts, and some only recieved a text message.

Frustration with the Amber Alert echoed sentiments expressed in New York last month when a similar alert woke up New York City residents in the middle of the night. A late-night Amber Alert was issued by the NYPD for a missing 7-month-old baby who was reportedly abducted by his mother, Marina Lopez.

The Amber Alerts are part of a Federal Communications Commission (FCC) program called the Wireless Emergency Alert (WEA), a cell phone program similar to the Emergency Alert System, which sends notifications to mobile devices. Amber Alerts were added to WEA in January. When activated, they send automatic messages based on proximity to phone numbers. 

The L.A. Times reported that the alert messages are sent through a special wireless carrier channel called Cell Broadcast, which have no texting charges. The system does not track the location of phones, yet it automatically sends alerts to all mobile devices in proximity of the alert. The program does not affect regular cell phone traffic.

Users can opt out of receiving alerts through their local providers.

Still, many California residents were confused about the alert, which had very few details about what was happening. Some users reported their message only included details about the blue Nissan and not the alleged kidnapper or victims.

James Lee DiMaggio reportedly murdered Christina Anderson of Lakeside, Calif., before kidnapping her children. Authorities said Anderson’s body was found Sunday night in Boulevard, a small rural community in eastern San Diego County, in a burned-down home. Police believe the children were kidnapped on Saturday around 5 p.m. and are still missing. DiMaggio is believed to be traveling north en route to Canada in the blue Nissan Versa with California license plate 6WCU986.

Hannah Anderson is described 5-foot-7, 115 pounds, with blonde hair and blue eyes. Ethan Anderson is described as 4-foot-11, 65 pounds, with sandy blond hair. DiMaggio is described as 5-foot-9, 150 pounds, with brown hair and brown eyes.

Police said anyone with information on the case should call the homicide detail at (858) 974-2321 or (858) 565-5200, or San Diego County Crime Stoppers at (888) 580-8477.

Amber Alerts, named in 1996 for 9-year-old Amber Hagerman, who was abducted and murdered in Arlington, Tex., are issued for abductions that meet specific criteria within each state. California’s Amber Alerts can only be issued if law enforcement believes a victim(s): has been abduction, is 17 years old or younger or has a proven mental or physical disability, is in imminent danger of serious injury or death, and if information that could assist the public is available.