DailyMail reports police were called to the Armstrong's home in Bellaire, Texas, about
2:15am on Friday. Dawn was found dead at the scene, while Antonio, 42 - who suffered a gunshot wound to the head - was rushed to hospital where he later died.
The couple's 16-year-old son has been charged with shooting his parents dead. The couple had two
other children, a 20-year-old son and a 12-year-old girl.
Houston police said they had yet to determine a motive.
'It was kind of the All-American family, that's why we're trying to get down to figure out what's going on in this household,' homicide detective Jimmy Dodson told KHOU.Investigators who searched the home found a smoking gun next to a note next reading,
'I've been watching you', according to KTRK.
'They're the family that everyone wanted to be like... her and Antonio together, they are what they call a power couple,' Dawn's cousin, Vaun Lee Armstrong told reporters.
'There was nothing left out. There was no neglect or anything. There was nothing that even could possibly have justified this situation.
'This doesn't even make sense. It makes no sense.'
Armstrong was a college All-American with Texas A&M in 1994, before being drafted in the sixth-round by the San Francisco 49ers.
In 1995, he played four games for the Miami Dolphins, while also spending three seasons in the CFL with the British Columbia Lions and Winnipeg Blue Bombers.
Since retiring, Armstrong went into motivational speaking, and opened a fitness company called 1st Class Training with his wife. They had three locations across Houston.
Former Texas A&M coach R.C. Slocum released a statement after learning of his former player's death.
'Antonio was a special young man. He was an All-American and an outstanding player, but he was an even better person,' Slocum said.
'He was such a positive influence on his teammates. He always had a great big smile and was a joy to coach.'