Police believed the exterior door to Zienkewicz's apartment was the door to Cairns' apartment. When Zienkewicz reached out for Silva, the officer, who Heckler said was about 100 yards away, fired four shots, assuming he was shooting at Cairns. Three shots hit Zienkewicz's door, Heckler said, and one hit her in the shoulder, killing her.
Silva, during a brief telephone conversation Thursday, said that Heckler's account was "not true" and that she wasn't outside during the standoff. Asked what happened, she said she did not remember and hung up.
Heckler said Silva and Cairns were highly intoxicated by alcohol or drugs during the encounter.
He called Zienkewicz's death a "tragic mistake," but said, "I have determined that under the circumstances of this case, the shooting by the officer was excusable."
The situation began around 4 p.m. Feb. 19, when police responded to a domestic-disturbance call at Cairns' unit at the Jefferson on the Creek apartment complex on East Street Road. Cairns' apartment was one of four attached units, two at ground level and two above. The exterior doors of all four units are in a row on the ground level.
Police found no evidence of a crime after the initial call and left, Heckler said. Though officers had been told there were guns inside, the weapons were not removed from the house, Heckler said.
Around 7:45 p.m., police received another 911 call, according to their records, from Silva. She said Cairns was trying to shoot himself.
According to records, soon after officers arrived, they heard shots hitting objects near them. Three of eight officers, including the one who fired the shot, took cover near a fence post, Heckler said.
Police spotted Silva, who was still on the phone with the 911 operator, wandering outside the four entrance doors, records say. Zienkewicz lived in the ground-level apartment below Cairns; her door was directly next to his.
Police records say it was too dark for the officers to read the numbers on the doors to confirm which was Cairns', and Heckler said Thursday calls were not immediately placed to the apartments to speak with either tenant.
As Silva stood in front of the doors, records say, police and the 911 dispatcher told her to move out of the area but she did not. Zienkewicz then opened her door and reached out to help Silva into her apartment, and the officer fired.
Heckler said the officer had "very good reason to believe that he was acting to end an immediate and critical threat to Ms. Silva" when he fired, and so he would not be charging him.
As for Cairns, Heckler said, "Under the law, he is responsible for the deadly consequences for the chain of events which he began." Cairns was charged with criminal homicide and other offenses.
Heckler said that Cairns fired at least 19 shots during the standoff, but that the shooting stopped just after the officer fired at Zienkewicz. Police therefore believed they had hit Cairns, only to discover Zienkewicz's body in the doorway several hours later.
Cairns barricaded himself in his apartment until around 2:30 the next morning, when he turned himself in. He is being held with bail set at $10 million.
Attempts to reach Zienkewicz's family and Cairns' public defender were unsuccessful Thursday.
Contact Chris Palmer at 609-217-8305, firstname.lastname@example.org, or follow on Twitter @cs_palmer.