4 people in custody over possible connection to sextuple homicide

Multiple persons of interest are in custody in connection with a sextuple homicide in Wisconsin that police believe was a targeted attack.

Six people were found dead inside a Milwaukee home after officers conducted a welfare check at the residence Sunday, police said. All victims -- five men and one woman -- had been shot, police said.

Four persons of interest are now in custody, though no one has been charged yet, Milwaukee Police Chief Jeffrey Norman said during a press briefing Thursday.

"We are still trying to determine what their involvement was, if any, in this homicide," Norman said.

Police believe there were "multiple suspects" involved in the incident. Evidence suggests that the shooting was targeted, and it does not appear to have been a murder-suicide, according to the chief, who said there is no threat to the public at this time.

The motive, exact time of the shooting and exact number of guns used in the shooting are still being determined, Norman said.

Milwaukee ABC affiliate WISN reported that it obtained court records that show that three of the six victims' names appear on a witness list for a pending homicide case in Milwaukee County Court.

When asked if that could be a reason why the victims were targeted, Norman told reporters that he believes it is unrelated to the incident, but that authorities are "looking into all angles."

"Obviously, you never want to use one explanation for a particular incident and stick to that," Norman said. "At this time, we're pretty sure that that is not relative to this particular incident, but we never want to take away any particular explanation for what we're finding in this investigation."

During their investigation, authorities discovered that a woman who claimed she was a victim of a shooting called 911 about 12 hours before the victims were discovered. Police do not believe that she was a victim of this shooting, and her possible connection to the incident remains under investigation.

The Milwaukee County Medical Examiner's Office identified the victims as Charles Hardy, 42; Caleb Jordan, 23; Javoni Liddell, 31; Donald Smith, 43; Donta Williams, 44; and Michelle Williams, 49.

Three of the victims lived at the residence, according to records from the medical examiner's office.

Acting Milwaukee Mayor Cavalier Johnson urged anyone with information in the case to come forward.

"It's time for that person to step forward, to come up, say something," he said during the briefing. "We can't have a city where somebody can go and pull the trigger and kill somebody, and then go sit on somebody's couch. We can't have that."

ABC News' Abigail Bowen contributed to this report.