Cook County State's Attorney Anita Alvarez said Thursday she has asked the FBI to help investigate the fatal shooting of two people by a Chicago police officer who was answering a domestic disturbance call on the West Side last weekend.



A law enforcement source has said Quintonio LeGrier, 19, was shot early last Saturday morning as he approached the officer, swinging a metal bat. Bettie Jones, 55, was shot by accident as she stood behind him near the front door of a two-flat in the West Garfield Park neighborhood.



The shooting is being investigated by the Chicago Independent Police Review Authority, but Alvarez said in a statement she has asked the FBI to join the case.



"This is a deeply disturbing incident that demands a very deliberate and meticulous independent investigation," she said in the statement. "At this stage, the investigation is being conducted by IPRA, but my office has also contacted the FBI to request their involvement as well."



She said her office "will review the results of the investigation when they are presented ... and will determine if any criminal charges are warranted."



Alvarez faced intense criticism for waiting more than a year to file murder charges against a Chicago police officer who shot and killed 17-year-old Laquan McDonald as the teen walked down the middle of a street with a knife in his hand. The officer fired 16 times, emptying his gun.



Alvarez filed the charges as the city of Chicago finally released a video of the October 2014 shooting. She has defended the investigation as a detailed inquiry into a case more complicated than the video might suggest, though she acknowledged the video's release spurred her to move up her announcement.