Two brothers from suburban Dallas made a murder-suicide pact which resulted in the death of six family members, according to the Allen Police.

Police responded to the scene after a phone call from "a concerned friend," at around1 a.m, who was worried that his friend was suicidal.

Police Sergent Jon Felty said, "The two brothers had entered into an agreement that they were going to complete suicide, and from that, it went to where the entire family was taken with them." 

"I've been here 21 years and we have never had an incident like this in the 21 years," Felty said.

Felty also said one of the brothers posted the link to a suicide letter on Instagram. "He goes into detail of what happened (would happen)," Felty said.

One of the brothers was 19 and the other was in his 20s. The other victim included a grandparent, their parents, and a twin sister to the 19 y/0.

Police identified the dead Monday as 54-year-old father Towhidul Islam; 56-year-old mother Iren Islam; 77-year-old grandmother Altafun Nessa; 21-year-old Tanvir Towhid; and 19-year-old twins Farben Towhid and her brother Farhan Towhid, according to NBC Dallas-Fort Worth.

Police said that the evidence suggests that the killings happened on Saturday.

Neighbors told they were stunned by the killing. They recall the family as a very happy family.