Aiyana Jones was shot and killed by police executing a search warrant as part of a homicide investigation, Assistant Chief Ralph Godbee said in a statement.
"This is any parent's worst nightmare," Godbee said. "It also is any police officer's worst nightmare. And today, it is all too real."
The warrant was executed about 12:40 a.m. ET Sunday at a home on the city's east side, Godbee said. Authorities believed the suspect in the Friday shooting death of 17-year-old high school student Jarean Blake was hiding out at the home. Blake was gunned down in front of a store as his girlfriend watched, Godbee said.
Preliminary information indicates that members of the Detroit Police Special Response Team approached the house and announced themselves as police, Godbee said, citing the officers and at least one independent witness.
"As is common in these types of situations, the officers deployed a distractionary device commonly known as a flash bang," he said in the statement. "The purpose of the device is to temporarily disorient occupants of the house to make it easier for officers to safely gain control of anyone inside and secure the premise."
Upon entering the home, the officer encountered a 46-year-old female inside the front room, Godbee said. "Exactly what happened next is a matter still under investigation, but it appears the officer and the woman had some level of physical contact.
"At about this time, the officer's weapon discharged one round which, tragically, struck 7-year-old Aiyana Stanley Jones in the neck/head area."
The girl was immediately transported to a hospital, where she was pronounced dead. Godbee said he and other officers went to the hospital while others stayed at the home to execute the warrant.
Aiyana's father, Charles Jones, told CNN affiliate WDIV, "She was sleeping and they came in the door shooting and throwing flash grenades ... burned my baby up and shot her, killed her."
Jones claimed the officers had the wrong house, but Godbee said in the statement the 34-year-old suspect in Blake's death was found and arrested at the home. In addition, a vehicle and a moped matching the descriptions of those involved in Blake's shooting were also found, he said.
The suspect's name was not released.
Godbee said he wished to "express to the family of Aiyana Jones the profound sorrow that we feel within the Detroit Police Department and throughout this community. We know that no words can do anything to take away the pain you are feeling at this time."
Police obtained the "high-risk search warrant" based on intelligence, and it was approved by the prosecutor and a magistrate, Godbee said. "Because of the ruthless and violent nature of the suspect in this case, it was determined that it would be in the best interest of public safety to execute the search warrant as soon as possible and detain the suspect ... while we sought a murder warrant," he said.
The police statement said Chief Warren Evans is out of town and could not be present "to personally address this tragedy," but "his thoughts and prayers are with the family and loved ones of Aiyana Jones."
The officer's weapon was secured, and an investigation is under way, Godbee said, emphasizing the information gained so far is preliminary.
"This is a tragedy of unspeakable magnitude to Aiyana's parents, family and all those who loved her," Godbee said. "... It is a tragedy we also feel very deeply throughout the ranks of the Detroit Police Department.
"We cannot undo what occurred this morning," he said. "All we can do is pledge an open and full investigation and to support Aiyana's family in whatever way they may be willing to accept from us at this time. I understand that they may not be open to such a gesture at this time, but we do stand ready to do anything we can to support them."