"Murder to the highest extent of the law would be more suitable to this case because this was my best friend. This was my best friend," Diamond Reynolds said.
St. Anthony police Officer Jeronimo Yanez was charged today with second-degree manslaughter in Castile's death. Ramsey County prosecutors also announced two additional felony counts of intentional discharge of a dangerous weapon that endangered the safety of the other two passengers in the car, Reynolds and her young daughter.
Castile, a 32-year-old elementary school cafeteria worker, was killed on July 6 during a traffic stop in Falcon Heights, a suburb outside of St Paul. The aftermath of the shooting was broadcast live on Facebook by Reynolds.
Reynolds said "nothing" can "fix the situation."
"At the end of the day, none of that is going to bring my boyfriend back," she added.
Reynolds said she believes she and Castile were "racially profiled" because they are black.
"If he were a white man, he would have been let go," Reynolds said of the fateful traffic stop. She pleaded with the public to not "forget Philando Castile."
Castile's family said it was "pleased" that the officer who killed him was charged today. His mother, Valerie Castile, thanked prosecutors and asked that demonstrators keep any protests peaceful.
"I’m just glad that we have come to this chapter and it’s the beginning to a different chapter," Valerie Castile said in a press conference this afternoon. "We all hope and pray that the right thing is done in this issue and I just want to thank everybody for coming out."
In the video broadcast on Facebook, Reynolds sits in the passenger seat of a car with Castile beside her in the driver's seat, his shirt apparently soaked with blood. Reynolds explains in the video that the officer "asked him for his license and registration."
Reynolds says in the video that Castile told the officer that the documents were inside his wallet and informed the officer that he had a pistol on him. "The officer said, 'Don't move.' As he was putting his hands back up, the officer shot him in the arm four or five times," Reynolds explains in the video.
A uniformed police officer can be seen in the video outside the car holding a gun. He is heard saying, "I told him not to reach for it. I told him to get his hand out."
Ramsey County Attorney John Choi noted in announcing the charges against Yanez that Castile's last words were that he was not reaching for the gun.
"Based upon our thorough and exhaustive review of the facts of this case, it is my conclusion that the use of deadly force by Officer Yanez was not justified and that sufficient facts exist to prove this to be true," Choi said at a press conference today. Castile had a legally permitted handgun with him, said Choi, adding that Castile "never attempted to reach for his gun."
Dennis Flaherty, executive director of the Minnesota Police and Peace Officers Association, said he is "disappointed" with the decision to charge Yanez and that he expects the officer to enter a not-guilty plea.
"Police officers in Minnesota and across the country face pressure of life-and-death situations daily," Flaherty said. "No one can speak for Officer Yanez as to what he actually encountered and what he feared that evening. We hope all people can understand that and can refrain from judgment."
Judge Glenda Hatchett, who is representing Castile's family in all civil matters, called the move to charge Yanez an "historic decision" in an "historic time."
"We see this [as] historic for the benefit that it has for this community, but we also see it as an important signal to this nation because of the series of shootings that we have seen across this nation," Hatchett said.
Castile's death prompted days of protests in Minnesota.
In a statement obtained by ABC News after the shooting in July, Yanez’s attorney, Thomas Kelly, said the incident had nothing to do with race.
"Officer Yanez has been completely cooperative with the investigation led by the Minnesota Bureau of Criminal Apprehension. He is deeply saddened for the family and loved ones of Philando Castile," Kelly said. "Tragically, the use of force became necessary in reacting to the actions of Mr. Castile. This heartbreaking incident had nothing to do with race. It had to do with the presence of a gun."
After briefly returning to limited duty, Yanez was placed on administrative leave in August.
Kelly did not immediately comment on today's announcement.
ABC News' Morgan Winsor contributed to this report.