Colin Kaepernick, the NFL’s original anthem protester, revealed the incident that inspired him to launch his notorious anthem protests in an interview with Paper magazine on Tuesday.

In the interview, Kaepernick pointed to a 2015 incident in San Francisco, where police officers shot and killed Mario Woods.

The police opened fire on Woods after he refused to drop a knife that he had allegedly used to stab a man. The incident gained national notoriety and was cited as an instance of excessive force by activists, because the officers had fired at Woods 26 times.

The officers were not charged in Woods’ death, and their actions were deemed to have fallen within SFPD guidelines at the time. A 90-second video of the incident can be seen here. In the footage, the police can be heard repeatedly demanding that Woods drop the knife.

However, Kaepernick called Woods’ death an “execution.” The former 49er went on to say that the incident prompted him to start reading about Malcolm X and other activist leaders throughout history.

“If Colin wasn’t reviewing a playbook, he was reading a history book,” Kaepernick’s girlfriend Nessa Diab 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,” TMZ Sports reports.

The City of San Francisco eventually reached a $400,000 settlement in the wrongful death lawsuit filed by Woods’ family. Colin Kaepernick never played in the NFL again.

Follow Dylan Gwinn on Twitter @themightygwinn