The Indianapolis Metropolitan Police Department said that a juvenile suspect had been identified and arrested by Monday morning. Since the suspect is a juvenile, the department did not release a name.
Detectives do not believe any additional persons were involved. No additional details about the arrest were released.
The victims killed have been identified as Kezzie Childs, 42, and Raymond Childs, 42, -- a mother and father -- as well as their children, 18-year-old Elijah Childs and 13-year-old Rita Childs.
Another woman, 19-year-old Kiara Hawkins, was also killed. She was pregnant with a baby boy who also did not survive.
"Yesterday, we promised swift justice for this heinous act. Today, we delivered on that promise," said police Chief Randal Taylor said in a statement. "While removing the alleged perpetrator of yesterday's mass murder from our neighborhoods does not bring back the lives senselessly lost, hopefully, it will bring us one step closer to healing as a community."
He continued, "I am grateful to all of the IMPD officers and criminal justice partners who have worked tirelessly for the last 30 plus hours to bring justice for these victims, their friends and families, and our entire community. I ask community members to join me in praying for the continued recovery of the young man whose life has been forever changed."
Indianapolis Mayor Joe Hogsett described Monday’s announcement about the arrest as, "the first step toward justice for the senseless acts that cut short the lives of six of our neighbors in the early hours of Sunday morning."
"While nothing can bring back the Childs family, I hope that the swift action of the Indianapolis Metropolitan Police Department offers some comfort to all of those who have been left to grapple with this tragic loss," Hogsett said in a statement provided to Fox News. "My thanks go to the men and women of IMPD whose thoughtful investigative work led to the arrest of the suspect, and my prayers are with the family, friends, and community impacted by this devastating act of violence."
The mass shooting happened at two separate addresses early Sunday morning and did not appear to be random, authorities said. Police first responded before 4 a.m. to the 3300 block of E. 36th Street to a report of a person shot.
That's where officers located a juvenile male with apparent gunshot wounds. He was transported to an area hospital and is expected to survive his injuries, police said.
Officers later "received information" that led them to a residence in the 3500 block of Adams Street, where five individuals were found with apparent gunshot wounds.
All were deceased, but, because one individual was pregnant, she was transported to an area hospital. Despite the best life-saving efforts provided by medical staff, both the female and the unborn child did not survive, the department said in an initial press release.
Homicide detectives responded to the scene and began their investigation. The Indianapolis-Marion County Forensic Services Agency responded to assist in identifying and collecting potential forensic evidence. The Marion County Coroner's Office will determine the exact manner and cause of death. The Marion County Prosecutors Office will review the case and determine a final charging decision.
IMPD spokeswoman Aliya Wishner said the juvenile arrested in the killings is not the same juvenile male who was found wounded Sunday before the victims' bodies were discovered, the Associated Press reported.
The Associated Press contributed to this report.