Police on Tuesday released the name of the 40-year-old woman shot and killed by an Ann Arbor police officer Sunday night.

Aura Rosser was fatally shot after police say she confronted officers with a knife inside a home in the 2000 block of Winewood of Ann Arbor, according to officials.

Rosser, of Ann Arbor, was shot once, according to Michigan State Police First Lt. Sean Furlong. Rosser's boyfriend, 54-year-old Victor Stephens, initially told The Ann Arbor News she was shot twice, once in the head and once in the chest.

Furlong wouldn't release where on her body Rosser was shot because the case is still under investigation. An autopsy was being performed Tuesday morning and any information about the official cause of death and details about the injuries likely wouldn't be released until it was complete.

Investigators wrapped up processing the scene Monday and were continuing to conduct interviews Tuesday, Furlong said. A toxicology report will also be conducted on Rosser to see if she was intoxicated at the time. The investigation could take weeks.

"We don't put a time table on these (investigations)," Furlong said. "Our main focus is to be thorough and complete."

Not much is yet known about Rosser. Messages left with family members were not returned. Stephens said he and the woman had been dating for about nine months and he believed she had a history of mental illness, but he wasn't able to elaborate. He said the woman had moved in with him so she could get away from Detroit and get some help in the Ann Arbor area.

Court records indicate Rosser had been convicted of shoplifting at a Pittsfield Township Kroger in 2012. She served 90 days in jail, the records indicate. In January 2013, Rosser was released from probation after being convicted of stealing a financial device and violating probation in Wayne County, according to records.

The use of deadly force is unusual in Ann Arbor, Furlong said, adding that that Ann Arbor police officers haven't used it at least since the 1980s.

"It doesn't happen very frequently in Ann Arbor," he said. "It's a very safe city."

Ann Arbor Police Chief John Seto was unavailable for comment immediately Tuesday morning, but told The Ann Arbor News he would look into the last instance an officer used lethal force.

Meanwhile, no information was being released about the Ann Arbor officer who fired the round that killed Rosser beyond an initial press release identifying the officer as male.

Furlong declined to release his name, deferring the question to the Ann Arbor Police Department.

Furlong did say the officer was immediately placed on administrative leave following the shooting Sunday night and that there was still ongoing discussion about his status Monday, but that the officer has not returned to active patrol.

Ann Arbor police officials have not yet released any information about the officer.

A press released issued by Ann Arbor police Monday said officers were called to the house for a domestic disturbance at 11:45 p.m. The officers were then "confronted by a woman armed with a knife," according to the release.

"One responding officer discharged his firearm striking the armed woman," the release said.

Furlong said police officers are authorized to use lethal force if they feel their own lives are in danger.

"An officer is allowed to use deadly force when there is an imminent threat to themselves or anyone else," he said.

The ultimate determination of whether lethal force is justified is made by prosecutors. Michigan State Police detectives will conduct their investigation, then hand over their findings to the Washtenaw County Prosecutor's Office, who could in turn hand it over to the Attorney General's Office if necessary, according to Furlong.

Officials have not yet released if officers responding to the scene were carrying Tasers or if there are either dashboard security video or audio recordings of the encounter that could play a part in the investigation.

Furlong said since the incident took place inside the house, it's unlikely patrol car cameras caught any significant footage. Most Ann Arbor officers are also equipped with audio recording devices on their person, though it's unknown at this point if the officer who shot Rosser was wearing one.

Stephens, Rosser's boyfriend, told The Ann Arbor News that lethal force wasn't warranted in this case.

"Why would you kill her?" Stephens said on Monday. "It was a woman with a knife. It doesn't make any sense."

Stephens said he initially called the police on Rosser because they were fighting and he wanted officers to escort her out of the house.

He said Rosser had a fish knife when police got there. Furlong would not release what kind of knife police believe it to be.

There were five people in the home when police arrived, according to Stephens.

City records show Stephens became the owner of the home last October, when the previous owner died and left it to him in a will. At that time, Michigan Department of Corrections records show Stephens was incarcerated as the result of a home invasion charge.

Stephens was released from prison in June of this year.

John Counts covers crime and breaking news for The Ann Arbor News. He can be reached at johncounts@mlive.com or you can follow him on Twitter. Find all Washtenaw County crime stories here.