Once you entertain the notion that social grievance entitles you to tread upon the rights of others, the difference between overrunning a mall and executing police officers is only a matter of degree.
On the same day that two New York City police officers were gunned down execution-style by a perpetrator who explicitly cited the deaths of Michael Brown and Eric Garner as his motivation, Black Lives Matter protesters in the Twin Cities overran the Mall of America in an organized trespass on private property. Protestors were warned days in advance that their planned demonstration was not welcome and would not be tolerated. Naturally, the protestors proceeded anyway.
Only 25 people were arrested. There should have been many, many more.
More links the protest at the Mall of America and the killings of Officers Rafael Ramos and Wenjian Liu in New York than their occurring on the same day. The commission of rights-violating protest, its endorsement by many within the culture, and its toleration by lawful authorities invite an escalation of violence. Once you entertain the notion that a sense of grievance entitles you to tread upon the rights of others, the difference between overrunning a mall, blocking traffic on an interstate, burning down a business, and executing police officers is only a matter of degree.
Consider how protest organizers justified their behavior at the Mall of America, as reported by the St. Paul Pioneer-Press:
Organizers and participants… said [the disturbance] was a necessary inconvenience to call attention to a critical issue.