The two officers backed away while telling him to drop the knife shortly before they each fired several rounds at Wallace, hitting him in the shoulder and chest.

Wallace's killing gained attention after a cellphone video of the incident was posted to social media platforms, where it went viral.

On October 26, 2020, police attended three separate times to Wallace's parents' house on the 6100 block of Locust Street in the predominantly black neighborhood of Cobbs Creek, Philadelphia.

[11][12] Around 3:45 p.m., during their third arrival, Officers Sean Matarazzo and Thomas Munz came in response to reports of a person screaming and a man assaulting an elderly female.

[16] Wallace then walked back into the street while Matarazzo and Munz continued to aim their guns at him, repeating for him to "put the knife down".

[4] Wallace's parents said officers knew their son was in a mental health crisis because they had been to the family's house three times on October 26.

[27][28] On October 30, the Wallace family reviewed footage from police body cameras worn by Matarazzo and Munz during the shooting.

Johnson stated that, based on the footage, Wallace was suffering from an "obvious mental health crisis" and he was incapacitated after the first shot.

"[23] The then-presidential nominee Joe Biden and his running mate Kamala Harris published a joint statement saying, "Our hearts are broken for the family of Walter Wallace Jr... We cannot accept that in this country a mental health crisis ends in death.

"[35] Protests and demonstrations against police brutality and institutional racism in response to Wallace's killing took place across Philadelphia throughout late October.

[37][38] According to Philadelphia officials, there was a total of 225 arrests, 60 injured police officers, 617 incidents of looting, 18 damaged vehicles, and 24 ATM explosions during the protests.

[23] Residents from several districts of Philadelphia were instructed by police to stay indoors to avoid "widespread demonstrations that have turned violent with looting".

[40] On October 30, Pennsylvania Governor Tom Wolf deployed the National Guard to Philadelphia and stationed them outside City Hall and the Municipal Services Building.

[42][43] Two men were charged with felony possession of weapons of mass destruction after illegal explosives, bolt cutters and machetes were found in their van.

The National Fraternal Order of Police posted a photo of a policewoman holding Young's son to Twitter and Facebook, claiming that the child had been found wandering the streets and that they were protecting him.