Colin Kaepernick says the 2015 shooting death of Mario Woods -- a black man who was shot multiple times by police officers -- is what compelled him to become a civil rights activist.
Colin told his story to Paper Magazine ... saying he was deeply affected by the incident, in which 26-year-old Woods was shot 21 times by 5 San Francisco PD officers during a Dec. 2, 2015 incident.
Cops confronted Woods -- who was holding a knife -- after receiving reports about a nearby stabbing.
Officers initially used non-lethal bean bag rounds on Woods while ordering him to drop the knife -- but then opened fire with live ammo when they claimed he became aggressive and was a threat.
But, cellphone footage posted after the incident appeared to contradict the police description -- showing Woods up against a wall while holding the knife at his side in a non-threatening manner.
A death investigation revealed Woods was shot 21 times -- 6 of those bullets struck him in the back.
The incident outraged citizens who accused the SFPD of executing Woods unjustly ... and according to Kap's girlfriend, Nessa, the QB began feeding his brain immediately after.
"If Colin wasn't reviewing a playbook, he was reading a history book," Nessa told Paper.
Kap took a knee in August 2016 -- 8 months after Woods' death -- and began his Know Your Rights Camp initiative that same year, using the Black Panther movement as inspiration.
Colin's KYRC has been thriving since their inception ... touching cities all around the country, and employing volunteers like Ava DuVernay, Taraji P. Henson and fellow NFL player Eric Reid.
Woods' family sued the City of San Francisco for wrongful death -- and ultimately struck a $400,000 settlement. The officers involved in the shooting were never charged with a crime after the D.A. said the shooting was justified because Woods "posed a credible threat."