A black man has been shot by US police after his wife called officers to their home to report a car-jacking.

In what the Indianapolis Metropolitan Police Department (IMPD) called a "tragic incident", the 48-year-old was reportedly mistaken for his wife's assailant by a police officer with nine years' experience.

The shooting, which has left Mr Williams fighting for his life in hospital, is the latest in a series that have sparked a crisis in the US over race relations and police training.

The fact Mr Williams, who reportedly had his gun on him, was shot on sight has prompted an outpouring of criticism.

Since promising greater transparency about police shootings, the IMPD has emulated police departments around the country by attempting to give a full account of the incident.

Speaking at a press conference broadcast on RTV6, assistant chief Randal Taylor said: "First and foremost this is a tragic incident, involving a homeowner attempting to protect his family and the IMPD officers trying to do the same thing.

"And of course our thoughts and prayers are certainly with the homeowner and the family, who was mistakenly shot by our officer and we wish him a quick recovery."

According to the account recorded by IMPD's dispatching team, Mr Williams called 911 at 4.34 am to report that his wife was assaulted by a "black male in a red shirt armed with a rifle" who had demanded their car keys before stealing the couple's black Nissan Sentra.

The road, Foxtail Drive, on the 3600 block, where Carl Williams was shot by police officer Christopher Mills after calling for help (Google Maps)

A disrupted phone line, in which the upset Ms Williams could be heard in the background, ended after four minutes with Mr Williams saying "is that him?" before cutting out. The dispatching team returned the call but only got through to voicemail.

This information was passed on by the dispatching team to officers. At no point did Mr Williams say he had a weapon.

Unarmed black care worker shot by US police while he was calming autistic patient

Two late shift officers were then sent to the area at 4.35am, arriving to find a black car with its headlights shining on the front drive. Assistant chief Taylor said police officers were trained to approach "quietly and tactically" rather than make their presence known.

As one officer began to check the number plate, Mr Williams opened the garage door while holding his own gun. The other officer, identified as Christopher Mills, then shot him in the abdomen.

Assistant chief Randal Taylor explains the sequence of events leading up to the shooting at a press conference (YouTube/RTV6)

Meanwhile, the original assailant is "still at large", said police.

Assistant chief Taylor continued: "They made observations based on information known at that time. The time of day, the early morning hours and low level lighting caused vision to be limited.

"The officers involved were forced to make a split second decision based on the information and totality of the circumstances known at the time.

"The officer involved was a nine-year veteran of the east district late shift. Again this was tragic and unforeseen. I don't know of any officer who goes out wanting to get into a shootout with anyone, but especially not as in this case a homeowner."

Protests and outrage across the US following killings by police Show all 19 1 /19 Protests and outrage across the US following killings by police Protests and outrage across the US following killings by police Protestors demand justice for Philando Castile on July 7, 2016 in St. Paul, Minnesota. Stephen Maturen/Getty Protests and outrage across the US following killings by police Protestors lie in an intersection during a demonstration for Philando Castile on July 7, 2016 in St. Paul, Minnesota. Stephen Maturen/Getty Protests and outrage across the US following killings by police Protestors lie in an intersection during a demonstration for Philando Castile on July 7, 2016 in St. Paul, Minnesota. Stephen Maturen/Getty Protests and outrage across the US following killings by police Protestors demand justice for Philando Castile on July 7, 2016 in St. Paul, Minnesota. Stephen Maturen/Getty Protests and outrage across the US following killings by police Protests and outrage across the US following killings by police Protesters march throughout New York City. Timothy A Clary/AFP/Getty Protests and outrage across the US following killings by police Protesters march throughout New York City. Timothy A Clary/AFP/Getty Protests and outrage across the US following killings by police Protesters are arrested by NYPD as they call for justice throughout New York City. Timothy A Clary/AFP/Getty Protests and outrage across the US following killings by police Protesters are arrested by NYPD as they call for justice throughout New York City. AFP/Getty Images Protests and outrage across the US following killings by police Protestors rally outside the White House in Washington, DC on July 7, 201. Black motorist Philando Castile, 32, a school cafeteria worker, was shot at close range by a Minnesota cop and seen bleeding to death in a graphic video shot by his girlfriend that went viral Thursday, the second fatal police shooting to rock America in as many days. / AFP / PAUL J. RICHARDS (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images) AFP/Getty Images Protests and outrage across the US following killings by police Protestors rally outside the White House in Washington, DC on July 7, 201. Black motorist Philando Castile, 32, a school cafeteria worker, was shot at close range by a Minnesota cop and seen bleeding to death in a graphic video shot by his girlfriend that went viral Thursday, the second fatal police shooting to rock America in as many days. / AFP / PAUL J. RICHARDS (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images) AFP/Getty Protests and outrage across the US following killings by police Demonstators rally in the middle of Times Square after they march through the city and call for justice for Alton Sterling and Philandro Castile on July 7, 2016 in New York. Black motorist Philando Castile, 32, a school cafeteria worker, was shot at close range by a Minnesota cop and seen bleeding to death in a graphic video shot by his girlfriend that went viral Thursday, the second fatal police shooting to rock America in as many days. / AFP / TIMOTHY A. CLARY (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images) AFP/Getty Protests and outrage across the US following killings by police Protestors gather outside the White House in Washington, DC on July 7, 201. Black motorist Philando Castile, 32, a school cafeteria worker, was shot at close range by a Minnesota cop and seen bleeding to death in a graphic video shot by his girlfriend that went viral Thursday, the second fatal police shooting to rock America in as many days. / AFP / PAUL J. RICHARDS (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images) AFP/Getty Protests and outrage across the US following killings by police Demonstators march through the city to call for justice for Alton Sterling and Philandro Castile as they rally in the middle of Times Square July 7, 2016 in New York. Black motorist Philando Castile, 32, a school cafeteria worker, was shot at close range by a Minnesota cop and seen bleeding to death in a graphic video shot by his girlfriend that went viral Thursday, the second fatal police shooting to rock America in as many days. / AFP / TIMOTHY A. CLARY (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images) AFP/Getty Protests and outrage across the US following killings by police Demonstators march through the city to call for justice for Alton Sterling and Philandro Castile as they rally in the middle of Times Square July 7, 2016 in New York. Black motorist Philando Castile, 32, a school cafeteria worker, was shot at close range by a Minnesota cop and seen bleeding to death in a graphic video shot by his girlfriend that went viral Thursday, the second fatal police shooting to rock America in as many days. / AFP / TIMOTHY A. CLARY (Photo credit should read TIMOTHY A. CLARY/AFP/Getty Images) AFP/Getty Protests and outrage across the US following killings by police Demonstrators gather at the Governor's Mansion in St. Paul, Minnesota, on July 7, 2016, to protest the latest shooting of a black man by police in Falcon Heights, Minessota. Philando Castile, 32, a school cafeteria worker, was shot by police after being pulled over while driving. The incident was captured in a video viewed by some two million people Thursday, as civil rights investigators probed a similar incident in Louisiana. / AFP / Joy Powell (Photo credit should read JOY POWELL/AFP/Getty Images) AFP/Getty Images Protests and outrage across the US following killings by police Getty Protests and outrage across the US following killings by police BATON ROUGE, LA -JULY 06: (EDITORS NOTE: Image contains profanity.) Protesters dance in the street near the convenience store where Alton Sterling was shot and killed, July 6, 2016 in Baton Rouge, Louisiana. Sterling was shot by a police officer in front of the Triple S Food Mart in Baton Rouge on Tuesday, July 5, leading the Department of Justice to open a civil rights investigation. (Photo by Mark Wallheiser/Getty Images) (Photo by Mark Wallheiser/Getty Images) Getty Protests and outrage across the US following killings by police BATON ROUGE, LA -JULY 06: Protesters march to the convenience store where Alton Sterling was shot and killed, July 6, 2016 in Baton Rouge, Louisiana. Sterling was shot by a police officer in front of the Triple S Food Mart in Baton Rouge on Tuesday, July 5, leading the Department of Justice to open a civil rights investigation. (Photo by Mark Wallheiser/Getty Images) Getty

The Black Lives Matter movement in the US has drawn attention to the disproportionate number of black Americans who are stopped, searched and shot by police.

Last month, a black therapist called Charles Kinsey was shot by police while lying unarmed on the ground with his hands in the air trying to calm his autistic patient. When he asked the police officer who shot him why he had done so, the man replied: "I don't know."

Other cases of black Americans killed by police last month include Philando Castile, 32, who was shot in his car when reaching for his wallet, and Alton Sterling, 37, who was repeatedly shot in the back and chest for carrying a gun in his pocket - as many people do in accordance with the US constitution's Second Amendment.