This is the first picture of a gunman who shot dead six at his girlfriend's party after not being invited to the bash.
Lt Joe Frabbiele said Teodoro Macias Jr was upset over not receiving an invitation to his partner's celebration.
Nubia Marquez, whose two brothers died in the shooting, said the 28-year-old suspect had a "serious" and "quiet" personality.
Macias took his own life after opening fire on the mobile home in Colorado Springs, US, where the family party was being held on Sunday.
Local police chief Vince Niski said the suspect showed 'power and control issues', adding that 'domestic violence' was at the core of the case.
Lt Frabbiele added: "When the suspect arrived, there were 10 family members present at the residence, seven adults and three children, ages two, five, and 11.
"We have recovered evidence showing that the suspect arrived at the residence alone, the suspect entered the residence and shot all six victims in quick succession.
"The suspect then shot himself shortly thereafter."
Resident Yenifer Reyes was woken up by the rapid gunfire, which she said sounded like a 'thunderstorm'.
Police officers discovered 17 shell casings at the scene after Macias reportedly emptied a magazine into the home.
An adult was able to flee the property unharmed, while three terrified children cowered inside.
Three teens who had temporarily left the party to collect something discovered a bloodbath when they returned, The Sun reports.
Police descended on the home and found Ms Marquez's brother Jose Gutierrez Cruz 'gravely' injured inside.
He was rushed to the hospital but could not be saved.
Ms Marquez said her other brother Melvin Perez, 30, also died in the shooting, along with her mum Joana Cruz, 53, Mr Perez's wife Mayra, 32, Mayra's sister Sandra Ibarra and brother Jose Ibarra.
Macias was Sandra's boyfriend, according to Ms Marquez and her husband Freddy.
