Peel Regional Police handout/CP Riya Rajkumar, 11, and Roopesh Rajkumar, 41, are seen in this undated police handout photo.

The alarms rang out in the middle of the night, triggered by a mother's urgent pleas to police to save her daughter hours after she celebrated her 11th birthday. Many jolted awake by the ringing of an Amber Alert hoped Riya Rajkumar, who was last seen with her father, would be found safe. Those hopes were dashed Friday when police found the child's body in the home of her father, who was later charged with first-degree murder. "It's very heart-wrenching," said Peel regional police Const. Danny Marttini, making particular note of the mother's pain. "We have to remember that this is a family, and she's now moving forward without her daughter."

Riya had just celebrated a joint Valentine's Day birthday with her mother before being dropped off at a gas station in Missisauga, Ont., on Thursday afternoon for a visit with her father, Roopesh Rajkumar, who did not live with them. When he failed to return Riya home at the scheduled time, Marttini said the mother became concerned. That anxiety morphed into something more serious after Rajkumar, an ex-boyfriend, allegedly indicated to the girl's mother that he planned to harm both himself and their child, Marttini said. "She came in already fully concerned saying, 'this is what he's saying to me, I'm concerned for the well-being of my daughter, I need some help,"' she said. Amber Alert led to arrest: police Marttini said police began investigating the situation right away, but did not immediately have grounds to enter Rajkumar's home, where Riya's body was found roughly five hours after she was reported missing. "We need extenuating circumstances to force entry into somebody's residence," Marttini said. "To do a door-knock? No problem. But if nobody answers, that's sort of as far as we go ... As the investigation unfolded, they did receive information that they did believe she was in the residence. As soon as they had that information, they proceeded." Shortly before entering the home, however, police had issued an Amber Alert in Riya's disappearance. The alert, released just after 11:30 p.m., was issued via the national Public Alerting System on cellphones across the province. That bulletin, police said, directly led to Rajkumar's arrest. Ontario Provincial Police Staff Sgt. Carolle Dionne said a motorist driving on Highway 11 in Oro-Medonte, Ont., shortly before midnight noticed Rajkumar's vehicle, which had been described in the Amber Alert.

THE CANADIAN PRESS/Andrew Ryan Local resident Jennifer Fuller places flowers at the scene outside of a house where a young girl was found dead in Brampton, Ont. on Feb. 15, 2019.

"As a result of the Amber Alert, they observed the vehicle and gave us the coordinates," she said. "Thankfully ... we were able to apprehend this man." When Peel police took custody of Rajkumar from the provincial force, Marttini said officers became aware of an undisclosed "medical condition" that meant he required treatment at a trauma centre. Rajkumar remained in hospital under police custody on Friday evening. Police declined to offer details on the cause of either Rajkumar's condition or Riya's death. As news of the girl's death spread, several people stopped by the area around Rajkumar's home to leave flowers and pay their respects. Related from HuffPost Canada: Ontario Police Can't Believe People Complained Amber Alert Woke Them Up

11-Year-Old Found Dead After Alleged Abduction By Father Emmanuel Okafor, who lives nearby, paused near the home, clasped his hands and said a silent prayer. "I pray to God the family lives through this," he said. "No family should ever go through this ... It breaks my heart." Okafor said he followed the situation closely after the Amber Alert was issued. "It's senseless," he said. "We were really hoping last night she would be found alive, not knowing this morning we'd have this tragic news." Jennifer Fuller, who has a daughter around the same age as Riya, laid flowers on a snowbank near the home. "It's sickening and it's sad," she said. 'Riya was a well-liked student' Grief and shock were also setting in at Meadowvale Village Public School in Mississauga, Ont., where Riya was a Grade 5 student. The school issued a statement expressing shock at the girl's "tragic" death, announcing flags would be lowered to half-mast, and outlining supports available to students. "Riya was a well-liked student, and her death is deeply felt by everyone at the school," Principal Stacy Service said. "Even students who did not personally know Riya will also be affected." Mississauga Mayor Bonnie Crombie called Riya's death "senseless," and Brampton Mayor Patrick Brown called the alleged killing a "horrific act."

Andrew Ryan/The Canadian Press Police monitor the scene outside of a house where a young girl was found dead in Brampton, Ont. on Feb. 15, 2019.