At a traffic stop near Minneapolis on Wednesday, he became the 123rd black American shot and killed by police in 2016, according to a Washington Post database that tracks such deaths.
Castile told police that he was "concealed and carry, that he was armed," his girlfriend Diamond "Lavish" Reynolds told reporters on Thursday. Reynolds was with Castile when he was shot and videotaped the immediate aftermath. The video was posted to Facebook and went viral on social media.
His mother Valerie Castile told CNN that her son had a permit to carry a concealed weapon, as did his sister.
About 1 in 17 eligible Minnesotans have a concealed carry permit, slightly more than the U.S. national average, according to gun rights advocates.
Hours before he was killed, Castile and his sister were discussing their carry permits when he stopped at the family home on his way to getting his hair styled, his mother told CNN.
"They were saying to be cautious. And my daughter said, 'I don't even want to carry my gun because I'm afraid they will shoot me first and then ask questions later,'" Valerie Castile told CNN.
Brian Herron, pastor at Zion Baptist Church in Minneapolis, said he was outraged that the shooting prompted comments that Castile was an upstanding citizen with no criminal record, rather than sparking immediate outrage that another black man had been killed by police.
"He didn't deserve to die. For a traffic stop? He didn't deserve to die. We're not animals. Why, in 2016, are we still talking about, 'I'm a man,' just like back in the 50s, 40s, 60s. Why do we have to keep saying, 'We're human?'" Herron said at a press conference.
Castile's Facebook page presented the image of an easy-going man who posted numerous photos of family members. It noted that he had studied at the University of Minnesota.
His background photo celebrates "Black Wall Street," a nickname for an affluent black community in early 1900s Tulsa, Oklahoma. The community prospered until 1921 when it was looted and burned by white rioters, according to the Tulsa Historical society.
St. Paul Public Schools, where Castile was employed in the Nutrition Services Department since 2002 when he was 19, said he was promoted to his supervisory position two years ago.
His employment started after he graduated with honors from St. Paul Central High School, where he was a straight-A student, his cousin Antonio Johnson told local media.
"Kids loved him. He was smart, over-qualified. He was quiet, respectful, and kind," a cafeteria co-worker said in a statement issued by the school.
Castile appeared to be a man on his way up in the world, his co-workers said.
"He wore a shirt and tie to his supervisor interview and said his goal was to one day 'sit on the other side of this table.'"