First, Trump dumps Obama's police reforms...

Jonathan Chait:

Last October, Minneapolis Police Union president Bob Kroll[above] appeared at a Trump rally. Clad in his red “Cops for Trump” T-shirt, Kroll (who has been alleged to be affiliated with white supremacists) gloated that the president had unshackled his officers from the restraints imposed by Trump’s predecessor. 

“The Obama administration and the handcuffing and oppression of police was despicable,” he told the crowd. “The first thing President Trump did when he took office was turn that around, got rid of the Holder-Loretta Lynch regime and decided to start takin— letting the cops do their job, put the handcuffs on the criminals instead of us”...

I Told Riot Cops I’m a Journalist. They Forced Me to the Ground and Pepper-Sprayed Me in the Face.

Cops face protesters, ignore looters

Kevin Drum:

The looters were completely unrelated to the protesters, who were generally peaceful. But there were hundreds of police officers facing off against hundreds of protesters, seemingly just waiting for a water bottle to be thrown so they could retaliate in force. 

Meanwhile, a few blocks away, TV helicopters showed looters destroying storefronts in precision formation with not a cop in sight. 

Since local law enforcement also has helicopters, I assume they knew perfectly well what was going on. They just didn’t feel like doing anything about it.

See also "When did cops become such cowards?"