Four people have been arrested in connection with the weekend slaying of an off-duty Chicago police officer, sources said Monday.

The suspects were apprehended after an armed standoff late Sunday at a home in the 7600 block of South Bishop Street in Auburn Gresham, according to a source with knowledge of the arrests.

Another source said SWAT officers responded to the home Sunday night searching for those involved in the killing of Officer Areanah Preston, 24, who was shot to death early Saturday in the 8100 block of South Blackstone Avenue while returning home from work.

No one has been charged, sources said. No other details were immediately available.

An autopsy found that Preston died from multiple gunshot wounds, the Cook County medical examiner’s office said Sunday.

Preston worked for the Chicago Police Department for three years and was assigned to the Calumet District. She was pursuing a master’s degree in criminology from Loyola University Chicago and would have graduated May 13.

It’s unclear why the police took more than 30 minutes Saturday morning to arrive at the scene after gunshots were detected by the city’s ShotSpotter gunshot surveillance system.

Police say Preston was shot to death around 1:42 a.m. The first notification of a person shot came more than half an hour later, at 2:15 a.m., according to Chicago Fire Department spokesman Larry Langford.

The fire department was alerted that someone had been shot when a police officer arrived and radioed that an off-duty officer had been shot, Langford said.

Less than a minute later, an ambulance and a paramedic-staffed fire engine were dispatched to the scene, and tey were both rolling less than a minute after that, Langford said.

But when the fire engine arrived at 2:23 a.m., the crew didn’t find anyone injured, Langford said. The police officer already had carried Preston to his squad car and rushed her to the University of Chicago Medical Center, where she died.

The police haven’t released a timeline of when officers were first dispatched to the crime scene.

Detectives canvassed the neighborhood the day of the shooting, asking neighbors for doorbell-camera video for the investigation.