Officials responded to a home around 1 a.m. after a family friend called authorities because they were concerned at least one person in the home was suicidal, WFAA reported.
When officers arrived, they found six people dead.
The family members were identified Monday afternoon.
- 54-year-old Towhidul Islam, father
- 56-year-old Iren Islam, mother
- 77-year-old Altafun Nessa, grandmother
- 19-year-old Farbin Towhid, sister
- 19-year-old Farhan Towhid, brother
- 21-year-old Tanvir Towhid, brother
The police department said investigators believe brothers Farhan and Tanvir made a pact to kill their parents, sister and grandmother before killing themselves.
"It appears that the two brothers had entered into an agreement," said Sgt. Jon Felty. "One of the victims put out a lengthy letter on his Instagram, and it kind of goes into detail about what he was feeling."
Felty said one of the brothers also wrote that all of his decisions were based on weighing pros and cons, including the decision to kill his family.
Friends describe the father as a former restaurant manager who recently worked in the cyber security field. The grandmother was visiting from out of the area, while an older son was a student at the University of Texas.
The youngest children are 19-year-old twins. Friends say that the daughter recently accepted a scholarship to New York University. Her brother recently dropped out of college.
"Inside the house, the children were unhappy for some reason, and one thing lead to another," explained Quamrul Ahsan with the Bangladesh Association of North Texas.
Several members of the organization gathered near the home after news of the family's death was released, the Dallas Morning News reported.
Ahmad Hossain, who lives about a block away, told the newspaper that the family moved to the area about seven or eight years ago from New York.
Hossain said Nessa, the grandmother, was visiting the family from Bangladesh. He said she was scheduled to return home last week but couldn't because of the COVID-19 pandemic.
Fazia Rahman, who graduated Allen High School last year with Farhan and Farbin Towhid, said the family was welcoming and the parents "treated everyone like they were their own kids."
"We don't want this to be their family legacy," she said. "They were such great people, they genuinely touched the lives of everyone who they came in contact with. ... They were good people who had bright futures ahead of them."
Police said their investigation is ongoing. There was no threat to the public.
If you or someone you know needs help, please reach out to the 24/7, free National Suicide Prevention Lifeline at 1-800-273-8255.
The Associated Press contributed to this report.