The father of an 11-year-old girl found dead at her dad鈥檚 home is to be charged with first-degree murder.

Peel police issued an Amber Alert after 11 p.m. Thursday, several hours after 41-year-old Roopesh Rajkumar failed to return his daughter, Riya, to her mother.

Riya was allegedly abducted by her dad after he took her out for her birthday Thursday afternoon.

Her father was arrested shortly after the discovery of her body, at around midnight on Thursday, and is expected to be formally charged Friday. Police revealed in a Friday afternoon update that Rajkumar has been hospitalized, in police custody, since his arrest.

The father made threats to harm his daughter and himself to his former girlfriend, Peel police spokesperson Danny Marttini told reporters Friday morning.

The girl鈥檚 mother alerted police at around 7 p.m. on Thursday, triggering an investigation to locate the two before the Amber Alert was issued.

"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,"' Marttini said. "Obviously our investigators took action right away."

The Grade 5 student did not live with her father on a full-time basis, police said, but was dropped off at a gas station in Mississauga, Ont., at about 3 p.m. so he and the girl could celebrate her birthday.

Riya shared a joint birthday with her devastated mother, Marttini revealed.

鈥淚t鈥檚 very heart-wrenching and that鈥檚 what we have to remember,鈥� Marttini said.

鈥淭his is a family and she is now moving forward without her daughter and it鈥檚 very traumatic.鈥�

Investigators located the girl鈥檚 body in her father鈥檚 Brampton, Ont. duplex about midnight.

Her father was arrested by Ontario Provincial Police in what has been described as a 鈥渉igh-risk takedown鈥� shortly after in Orillia, Ont., about 130 kilometres north.

Rajkumar is currently in hospital and will appear in court once he is medically cleared, police said.

鈥淲hen we did take custody of the individual鈥� our officers at that time did notice that there was a medical concern,鈥� Marttini explained. 鈥淭hey were concerned about his wellbeing. At that point, that individual was taken to hospital.鈥�

Tips from citizens responding to the alert led to his arrest, say police.

Peel police confirmed that Riya was found dead at the scene. Officers did not initially enter Rajkumar鈥檚 Brampton home when they saw that his vehicle was not there.

Reporters raised questions about why it took so long to issue the Amber Alert. Marttini said there will be a review.

Meanwhile, forensics teams are combing the Brampton home for evidence.

鈥淭his is very hard for everyone that鈥檚 been involved in the case and the family that are having to deal with this,鈥� Marttini said.

Speaking to CTV Toronto, one of Rajkumar鈥檚 relatives said that nothing about the accused suggested that he could be violent.

鈥淗e was always a cousin to look up to,鈥� Ryan Ali said. 鈥淲e just never expected this to happen.鈥�

CONDOLENCES POUR IN

At Riya鈥檚 elementary school -- Meadowvale Village Public School in Mississauga -- flags stood at half-mast on Friday and grief counsellors were called in to talk to students. In front of the Brampton home where the little girl鈥檚 lifeless body was found, mourners brought flowers and stuffed animals.

Prime Minister Justin Trudeau said Amber Alerts were critical in police investigations when a child鈥檚 life is in danger.

鈥淎mber Alerts like the one so many of us received last night are critically important to helping police when a child鈥檚 life is on the line,鈥� .

鈥淢y deepest condolences to everyone mourning young Riya today.鈥�

Ontario Premier Doug Ford that he was hearbroken for Riya鈥檚 mom who is living 鈥渆very parent鈥檚 worst nightmare.鈥�

鈥淎s a father to four daughters, I鈥檓 truly at a loss for words,鈥� he wrote.

鈥淜arla and I are keeping Riya鈥檚 family and community at Meadowvale Village Public School in our prayers.鈥�

Mississauga mayor Bonnie Crombie said Riya鈥檚 鈥渟enseless鈥� death made her 鈥渟ick to her stomach鈥�.

鈥淭here are no absolutely words to explain the senseless and tragic loss of young innocent Riya,鈥� she wrote.

鈥淎s a mother of three, this makes me sick to my stomach. My heart grieves for the mother and family. May the apprehended suspect see the full weight of the justice system brought before him.鈥�

With files from The Canadian Press