PHILADELPHIA — Relatives of Walter Wallace Jr., who was fatally shot this week by police officers while wielding a knife and struggling with his mental health outside his West Philadelphia home, met with Police Commissioner Danielle Outlaw and other city officials Thursday to view body-worn camera footage of his killing, according to the family’s attorney.Speaking at a news conference outside City Hall in the afternoon, the Wallace family’s lawyer, Shaka Johnson, said the footage of the shooting was brief. But according to Johnson, it showed Wallace “in obvious mental health crisis,” with offi…