CHICAGO >> An argument in a house on Chicago’s South Side erupted into gunfire early today, leaving four people dead and four more injured, police said.

The shooting happened at about 5:45 a.m. in the Englewood neighborhood, police said. No one has been arrested and police provided few details about the shooting. None of the victims appeared to be juveniles.

At a news conference this morning, Police Superintendent David Brown said three of the victims who died were female and one was male. The department earlier reported that all four were female.

Detectives were trying to determine if there was more than one shooter, police spokesman Tom Ahern said. A 2-year-old child was removed safely from the house and placed in protective custody, he said.

Authorities have not released the identities and ages of the four who died.

The injured included two men who were shot in the back of the head. Police were unable to provide information on their conditions. A 23-year-old man who was shot in the back and a woman who suffered an unspecified gunshot wound were both in critical condition, police said.

Brown said detectives haven’t been able to interview the four surviving victims, who were being treated at hospitals. But he said a witness told police there were gunshots at about 2 a.m. and that the department’s ShotSpotter gunfire detection system picked up the sound of gunfire at that time. Brown did not provide any details about whether that gunfire was related to the shooting at the house. The witness told police more gunshots rang out at about 5:45 a.m.

Brown also said the police received several calls about disturbances at the residence, but did not elaborate. He said a high-capacity magazine and shell casings were recovered from the scene and that there was no apparent forced entry.

The shooting comes a few days after a woman was killed and nine other people were injured when two men opened fire on a group standing on a sidewalk in Chatham, also on the city’s South Side. Police said no one has been arrested in that shooting. Several mass shootings over the weekend have stoked concerns about a spike in U.S. gun violence heading into the summer, as coronavirus restrictions ease and more people are free to socialize.

A database compiled by The Associated Press, USA Today and Northeastern University that tracks mass killings — defined as four or more dead, not including the perpetrator — shows today’s shooting in Chicago is the 18th mass killing, of which 17 were shootings, so far this year in the U.S.

Englewood has long been one of the most violent communities in Chicago, and the city has experienced more homicides this year compared with the same period last year. There were 282 homicides in Chicago as of June 13, compared with 269 during the same period last year.

Chicago Mayor Lori Lightfoot told reporters that the city needs federal help to combat violence and said the White House had reached out to offer assistance.

“We must acknowledge this for what it is — a tragedy that’s ripped apart families and inflicted intense trauma,” Lightfoot said.

Lightfoot was one of 27 mayors to sign a letter to President Joe Biden from the United States Conference of Mayors “urging immediate action” to combat gun violence and the flood of illegal guns pouring into their cities.

“There are too many guns on our streets and we need a federal and nationalized strategy in order to deal with this, just like the Biden administration dealt with COVID-19,” said Houston Mayor Sylvester Turner during a video news conference.

They asked the White House to “take a leadership role in enacting meaningful and common-sense gun control legislation,” push for universal background checks and a ban on assault weapons.

Perhaps recognizing there is little chance that Congress will pass much of the legislation they support, the mayors also asked Biden to take as many steps as he can that don’t require Congressional approval.

“The administration has to fully empower the (Bureau of Alcohol, Tobacco, Firearms and Explosives) to go after federally licensed gun dealers who we know are selling to straw purchasers,” Lightfoot said, referring to the practice of buying guns legally and selling them to those who cannot legally own firearms.