Police have identified four family members who were found dead inside a Markham, Ont. home on Sunday night.

Officers were called to a residence on Castlemore Avenue shortly before 3 p.m. after receiving reports of multiple people injured inside.

When officers entered the home, they found four people dead. The victims have been identified by investigators as 21-year-old Malesa Zaman, 59-year-old Moniruz Zaman, 50-year-old Momotaz Begum and 70-year-old Firoza Begum.

(From left to right) Malesa Zaman, 21, Moniruz Zaman, 59, Momotaz Begum, 50, and Firoza Begum, 70. (Facebook)

Police said that a 23-year-old man met officers at the front door and was immediately taken into custody. A source has confirmed to CTV News Toronto that the victims were the suspect’s sister, father, mother and grandmother.

In a news release issued Wednesday afternoon, York police said they have determined the cause of death, but “will not be released in this investigation to protect the integrity of the case before the courts.”

According to friends, Momotaz Begum and Moniruz Zaman had just celebrated their 25th wedding anniversary. They have been described as a “very nice, quiet, decent happy family.”

One family friend said that he has a hard time believing their son may be responsible for their deaths, saying he made a “beautiful slide show” for his parents’ anniversary party.

“He talked more than 20 minutes about the parents, how good their life is…he was a pretty ordinary, gentle kid, happy family. No clue how come this happened,” Robin Islam told CTV News Toronto.

Moniruz Zaman, 59, and Momotaz Begum, 50, celebrate their 25th wedding anniversary. (Photo provided by friends)

Sabrina Saltana considered herself one of Momotaz Begum’s best friends and said they often met up for coffee, movies and to go shopping.

“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.”

“How is this possible?”

Saltana said that Momotaz Begum was always praising her son and saying how proud she was of him.

“She always said ‘my son is really good, my son goes to the mosque.’”

CTV News Toronto has learned that Moniruz Zaman was an employee with Beck Taxi and Malesa Zaman was a part-time worker at a local grocery store.

York Regional police officers stand outside of a home in Markham, Ont. on Sunday, July 28, 2019. (The Canadian Press / Alanna Rizza)

An online gamer has said that the accused reportedly sent users disturbing comments detailing the killings, and that an administrator notified police.

Maroon, a user identified as an administrator of “Perfect World Void,” said that the community was “very saddened by the incident.”

“One admin was the first of the people who contacted the cops regarding the case, without the exact address unfortunately,” Maroon wrote. “Then after some digging by one of our players, who was able to find his address, the police were informed.”

Menhaz Zaman is pictured in this court sketch on July 29, 2019. (Pam Davies/ CTV News Toronto)

Menhaz Zaman has since been charged with four counts of first-degree murder in connection with the quadruple homicide.

Police have said they are not looking for any additional suspects in the case.

Menhaz Zaman is scheduled to appear in court on Aug. 5