Dhaka, April 6 -- Police believe Farhan Towhid, 19, and his older brother, 21-year-old Tanvir Towhid, carried out the carnage Saturday at the family's home in Allen, according to Fox 4.

All six victims of the Bangladeshi family - including the brothers' parents, sister and grandmother - were discovered by police dead with gunshot wounds during a wellness check at about 1 am on Monday.

A friend of Farhan's told police about a rambling suicide note Farhan had linked to from Instagram, detailing how he and his brother hatched the plan in February to kill their family and themselves if they could not "fix everything," CBS DFW reported.

Both brothers, who attended UT Austin, battled depression, the note said.

"The plan was simple. We get t...