Mohamed Noor, 33, was convicted of third-degree murder and second-degree manslaughter for killing 40-year-old Justine Ruszczyk Damond outside her home near Minneapolis, in an incident that drew global criticism including from Australia's prime minister, who called the incident "shocking".
The jury found Mr Noor's shooting of Ms Damond was not justified under the circumstances.
This case is the second time an officer was charged with killing someone while on duty, and believed to be the first such conviction.
Noor's lawyer said a "perfect storm" of events led him to open fire on Ruszczyk the night of July 15, 2017, when she called 911 to report a possible assault in progress in an alley behind her Minneapolis home.
A jury of 10 men and two women took less than one day to reach their verdict. Police officers Mohamed Noor and Matthew Harrity responded.
Prosecutors questioned whether the loud bang was real, pointing out that neither Noor nor his partner initially mentioned anything at the scene about hearing such a noise. Noor testified that he could identify Ruszczyk as a threat, raising an arm standing outside of the driver's side window.
It's rare for police officers to be convicted after asserting they fired in a life-or-death situation, but some Minnesota community members said they saw it coming for Noor because he is Somali American.
Noor was taken out of the courtroom in handcuffs and into custody, according to U.S. media reports.
Noor reportedly did not react to the verdict, while Damond's fiancé Don Damond became emotional when the verdict was read out.
Elon Musk reaches SEC agreement on his Twitter usage
Securities and Exchange Commission on Friday over his use of Twitter , according to a filing in Manhattan federal court . Tesla's $1.8-B junk bond fell to yield 8.42%, more than 3 percentage points above the bond's coupon rate of 5.3%.
Noor, a two-year veteran who testified that he shifted to policing from a career in business because he "always wanted to serve", was acquitted of the most serious charge of intentional second-degree murder. Defense attorneys labeled Noor a hero, saying he was just trying to save his partner's life. Sentencing is scheduled for June 7.
A Minneapolis jury has found a former police officer guilty in the 2017 fatal shooting of an unarmed woman minutes after she had called 911 to report a possible crime.
"That night there was a tragic lapse of care and a disregard for the sanctity of life", Damond said.
In an email to 5 EYEWITNESS NEWS, Minneapolis Police Officers Federation president Lt. Noor, a 33-year-old muslim immigrant from Somalia, was a two-year veteran of the force at the time of the shooting.
The Hennepin County Sheriff's Office said it had concerns about Noor's safety if he was free.
Stinson's records show that since 2005, there have been just 98 law enforcement officers charged with murder or manslaughter in the United States.
Some activists argue that in charging Noor, who's Somali, prosecutors are scapegoating him.
Minnesota's third-degree murder charge means causing the death of another through a unsafe act "without regard for human life but without intent to cause" death. They are sequestered until reaching a verdict.