"I can't imagine what kind of evil it takes to shoot two women and the innocent children in their arms," Police Chief Michael Spears said at a news conference.
The other victims were Jordan Hunt, 23 months; his mother, Gina Hunt, 24; and Charlii's mother, Andrea Yarrell, 24.
Police said they had identified people they wish to question and were looking for them, but they would not name the people or describe them. Two handguns were found within a block of the house, where all four of those killed lived, said Sgt. Matthew Mount, a police spokesman.
"Whoever is responsible for this, we're going to track you down like dogs," Marion County Sheriff Frank Anderson said. "We're not going to stop until we find you and put you in a cage where you belong."
Annie Boyd, the mother of Andrea Yarrell's boyfriend, told The Indianapolis Star that her son heard a gunshot while he was on the phone with Yarrell.
Gene Boyd, who is in the Indianapolis Men's Work Release Center on charges in a drug case, told his mother he heard someone break into the home.
"He heard the shot, then heard Gina holler out: 'Those are my babies!'" Annie Boyd said. "After that the phone went dead."
Gene Boyd then called his mother, who called 911.
A set of scales, several weapons, a safe and one pound of a what is believed to be marijuana were found in the house, Talley-Sanders said. She said police had been called to the home three times in 2007 to investigate reports of armed robbery, burglary of a resident and a stolen vehicle.
"There's just a number of factors that have to be looked at," Mount said. "Because of the things that were found at the scene they are going to look at every possible motive."
Gina Hunt was arrested in a suspected bad check scheme in 2002. The Associated Press was unable to determine the outcome of that case Tuesday.
Yellow crime scene tape cordoned off nearly a half block of the street, lined with modest brick and frame houses. At the small one-story white house where the slayings occurred, officers inspected the frame of the open front door.
As word of the shootings spread, neighbors gathered to watch investigators. The front entrance to the home was flanked by signs reading "Peace on the streets, stop the violence," and stuffed animals were piled on the steps and the bushes.
Janice Turner, 46, of Indianapolis, said she stopped at the house to pray.
"It's sickening. I'm tired of people messing with these babies," Turner said.
Community activists and religious leaders encouraged people with information about the crime to come forward.
"When things happen, people need to come together as a community and be nosy neighbors," said Michael Wolley, a chaplain with the sheriff's department. "On the streets there's a code of silence, and we need to break that because enough is enough."