York Regional Police have formally identified the four members of a family who were found dead inside a Markham home last week.

Police were called to the home on Castlemore Avenue near Mingay Avenue shortly before 3 p.m. on Sunday, July 28 for a report that multiple people may have been injured at a home.

Sources close to the investigation previously told CTV News Toronto that police were alerted to the situation by citizens concerned about postings on the murders, allegedly written by the suspect on gaming websites. 

Officers arrived and were greeted at the front door by a man who was taken into custody.

Four people were subsequently found dead inside the home.

Police have now formally identified them as 70-year-old Firoza Begum, 50-year-old Momataz Begum, 59-year-old Moniruz Zaman, and 21-year-old Malesa Zaman.

A source previously confirmed to CTV News that the victims are the suspect's grandmother, mother, father and sister, respectively.

Police said Wednesday that the cause of death has been determined through autopsies, but police are not yet disclosing how the victims died.

Menhaz Zaman, 23, has been charged with four counts of first-degree murder.

He is scheduled to make a court appearance on August 2.

The formal identification comes as new details emerge about the victims.

Friends told CTV News Toronto Wednesday that Momotaz Begum and Moniruz Zaman had just celebrated their 25th wedding anniversary and that the family was "very nice, quiet, decent, happy."

Sabrina Saltana said that Momotaz Begum was more than just her best friend and she is struggling to understand how something like this could have happened.  

“Not only best friend, she is also like a sister too,” Saltana said. “To be honest, I’m shocked. I feel like I’m not in the world, I’m somewhere else. My whole body is like, I think I’m flying.”

Saltana said that Begum was a proud mother who spoke about having a "good" son who attended mosque.

Another family friend, Robin Islam, said that Menhaz Zaman spoke about his parents for 20 minutes at their anniversary celebration and made a slide show for the occasion.

"He was a pretty ordinary, gentle kid. Happy family – no clue how come this happened,” Islam said.

Beck Taxi has said that Moniruz Zaman had been an employee with the company since 2011 and said they were "devastated" by his death.