Here's what we know and don't know about the case of an Upper Deerfield Township man shot by state police after troopers were sent to the wrong house to investigate a 911 hang-up call.

How did police end up at the wrong house?

Around 11:30 p.m. Friday police dispatchers in Cumnerland County received a 911 call, but the caller hung up. An attempt was made to trace the call so police could be sent to the location where the call originated and check on the well-being of the caller.

Gerald Sykes, seen in this undated photo, was shot and wounded by state police at his Upper Deerfield Township home late Friday night, authorities say. (Submitted Photo)

The trace came back to the home of Gerald and Margot Sykes in the 300 block of Centerton Road, authorities said. That was not, however, the location from where the call was made, but two uniformed state troopers from the Bridgeton Station were sent to that address not knowing it was the wrong one.

Officials have not yet explained how the mixup in addresses happened, if this is something that has happened before or if the correct address for the 911 hang-up call was located and police dispatched to that location.

How could the confusion have resulted in gunfire?

While it is not mentioned in the Attorney General's Office's initial report, the troopers likely did not use lights or sirens when responding to the Sykes' home, according to police protocol.

"Lights and sirens are not required at time of arrival in response to many types of calls because that could work against the safety and effectiveness of police officers responding to an unknown situation," said New Jersey State Police Captain Stephen Jones.

The troopers arrived at the Sykes home around midnight.

The Attorney General's report says the two troopers "approached the home and knocked in an attempt of communicate with the occupants."

They received no response so they went around back to a deck and "knocked, shining flashlights into the home and announcing that they were responding to a 911 call.

A friend and attorney for the family, Rich Kaser, said that the Sykes were asleep and a barking dog woke them up. Sykes went into the living room where he saw someone through the French doors outside on his deck, Kaser said. Sykes went back to his bedroom, got his shotgun and returned to the living room.

At that time where was an exchange of gunfire ... in which one of the troopers fired four rounds from his service 9 mm handgun and Gerald Sykes fired a single round from a shotgun."

According to Sykes' relatives, Sykes and his wife heard no announcement that the shadows outside the door to their deck were state troopers.

Who fired first?

Asked who fired first, the Attorney General's Office in an email response, said that is part of the ongoing investigation and it couldn't comment.

Kaser said that it was police who fired first.

Family said Sykes was hit by three of the four shots fired from outside into the house through the French doors with glazed glass. They said Sykes collapsed after being hit, but managed to get one shot off from inside the home through the window out to the deck.

How is the victim doing?

After being shot, Sykes eventually came out of his house and was put face-down on the ground and handcuffed, according to Kaser. The AG's Office declined to comment on that accusation.

On Monday Sykes remained in stable condition at Cooper University Hospital, Camden, where he was airlifted to after the incident. Kaser said Monday afternoon Sykes had been moved out of intensive care and into a regular hospital room. Sykes was still in a lot of pain, Kaser said, but doing well considering what he had gone through. "He will make a recovery," Kaser said.

What happened to the troopers?

The Attorney General's Office says that one trooper received a graze wound from either flying glass or from the blast from the shotgun that Sykes fired. Both troopers -- the one injured and the one uninjured -- were taken to Inspira Medical Center Vineland to be treated.

Neither trooper was identified. Both are now on paid administrative leave.

What is the reaction to the case?

Kaser called the incident a "tragic mistake." He said Sykes, 76, had been a longtime South Jersey resident living in Gloucester County before moving to Cumberland County.

"Why was the first response to pump four rounds through a door?" son-in-law Ronald Lafalce asked in an interview with 6ABC.

The family members said Sykes was hit by three of the four shots fired by one of the troopers.

"Twice in the chest. Once in the groin. Collapsed lung. Internal bleeding," said Diana Lafalce, Skyes' stepdaughter added, describing the injuries Sykes had suffered.

How long will the investigation take?

Because it was a police-involved shooting involving the New Jersey State Police, the New Jersey Attorney General Office's Shooting Response Team is handling the probe. The Attorney General's Office said Monday there was no new information that could be released on the case and, a spokesman said, there is no timeframe for the investigation to be completed and its results made public.

Bill Gallo Jr. may be reached at bgallo@njadvancemedia.com. Follow Bill Gallo Jr. on Twitter @bgallojr. Find NJ.com on Facebook.