Indianapolis police arrested a 17-year-old boy Monday in the killings of five people, including a pregnant woman, who were shot to death inside a home in what the city's mayor called a "devastating act of violence."

The Indianapolis Metropolitan Police Department said in a statement that the name of the suspect in Sunday's killings was "not being released at this time since the suspect is a juvenile." No one else was believed to be involved, police said.

Police said Sunday that the fatal shootings were discovered by police who had been called about 4 a.m. Sunday to investigate reports of a person shot on the city's near northeast side and first found a juvenile male with gunshot wounds.

As officers were investigating, police received information about 4:40 a.m. that led them to a nearby home, where they found multiple adults dead inside from apparent gunshot wounds, Sgt. Shane Foley said Sunday.

IMPD spokeswoman Aliya Wishner said Monday that the suspect in custody is a 17-year-old boy who is not the same juvenile male who was found wounded Sunday before the victims' bodies were discovered.

Michael Leffler, a spokeswoman for Prosecutor Ryan Mears, said in response to a request for comment on what charges the suspect might face, and if he would be waived into adult court, that the office "can only confirm what IMPD has already released at this time."

Police Chief Randal Taylor said Monday in a statement announcing the arrest that he was asking the community to pray for the recovery of the juvenile male found wounded Sunday, saying that his "life has been forever changed."

Foley said Sunday that police believe that juvenile, whose age has not been released, was wounded in the same shootings that left the five others dead, along with the unborn child.

Kezzie Childs, 42, Raymond Childs, 42, Elijah Childs, 18, Rita Childs, 13, and Kiara Hawkins, 19, and the unborn child of Hawkins were pronounced dead after being found in the home, the Marion County Coroner's office said. Hawkins was first taken to an area hospital, but both she and her unborn male child died despite life-saving efforts, authorities said.

Police did not release details Sunday of the relationships between the shooting victims, and Wishner said Monday afternoon that information was not yet available because the case is currently under seal in a Marion County court.

But Mayor Joe Hogsett referred to the victims as "the Childs family" in a statement thanking Indianapolis police for their quick arrest of a suspect.

"Today's announcement is the first step toward justice for the senseless acts that cut short the lives of six of our neighbours 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.

"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," he said.