He added: "When he [Macias] wasn't invited to a family gathering, the suspect responded by opening fire".
Police confirmed that none of the children were injured in the attack.
Family, friends and children were celebrating a birthday inside a trailer at the Canterbury Manufactured Home Community, a mobile home park of largely Latino residents in southeast Colorado Springs, about 70 miles (110 km) south of Denver.
"My vow to this community and to the families who have lost someone today, is that this department will do everything we can to find you the answers you deserve and be here for you with an unwavering support", Niski said in the police statement.More news: India sees 403000 new virus cases, 4092 deaths in 24 hours
The Colorado Springs Police Department identified the victims as Melvin Perez, 30, his wife, Mayra Ibarra De Perez, 33, his mother, Joana Cruz, 52, and his brother, 21-year-old Jose Gutierrez. Preliminary investigations revealed that families had gathered for a birthday party inside one of the trailers when the shooting occurred.
'Multiple lives were taken today by this awful act of violence.
Police said the shooter used a 9mm semi-automatic handgun that was equipped with two 15-round magazines.
The suspected shooter - believed to be a boyfriend of one of the victims - is also dead, according to Colorado Springs Police.
Authorities were not sure how Macias came to possess the weapon.More news: Boris Johnson hails Conservatives' crushing win in U.K. Labour stronghold
Authorities received three 911 calls shortly after the shooting.
There no previously reported or newly discovered incidents of physical altercations from the year-long relationship, said the lieutenant. One call originated from inside the home and captured rapid gunfire. The firearm was purchased by someone in 2014 from a local gun store, Frabbiele said. One of the family members escaped the scene and made the third call.
Reyes has lived in the neighborhood for three years.
"In Colorado, we've had domestic terrorism incidents where lots of people were killed, we've had random acts like going into a King Soopers or a movie theater, but let's not forget about the lethality of domestic violence", Colorado Springs Mayor John Suthers said.More news: 4 police officers indicted on federal civil rights charges — George Floyd case