The Baltimore Sun has a timeline of the basic events:
It started Monday morning with word on social media of a “purge” — a reference to a movie in which crime is made legal. It was to begin at 3 p.m. at Mondawmin Mall, then venture down Pennsylvania Avenue to the Inner Harbor.
With tensions in the city running high on the day of Freddie Gray’s funeral, police began alerting local businesses and mobilizing officers...
Ultimately, not much happened, at least compared to historic riots, so the story that the "city" rioted, is false, as Jamelle Bouie notes:
On Monday night, there were riots in Baltimore, but it’s hard to say Baltimore was rioting. This wasn’t 1968, when fires touched huge swaths of the city and thousands left their homes. Instead, in a few areas around the Inner Harbor and East and West Baltimore, scattered groups of looters smashed stores, set fires, and confronted police, with residents watching from stoops or out of windows.
As with Ferguson, this is likely violence begetting violence, as a history of police abuse comes to a head at one death. A few months back, the Sun itself covered the history of police brutality in the city:
The city has paid about $5.7 million since 2011 over lawsuits claiming that police officers brazenly beat up alleged suspects. One hidden cost: The perception that officers are violent can poison the relationship between residents and police.
...
City policies help to shield the scope and impact of beatings from the public, even though Mayor Stephanie Rawlings-Blake acknowledges that police brutality was one of the main issues broached by residents in nine recent forums across Baltimore.The city’s settlement agreements contain a clause that prohibits injured residents from making any public statement — or talking to the news media — about the incidents. And when settlements are placed on the agenda at public meetings involving the mayor and other top officials, the cases are described using excerpts from police reports, with allegations of brutality routinely omitted. State law also helps to shield the details, by barring city officials from discussing internal disciplinary actions against the officers — even when a court has found them at fault.
Regardless of whether and how this history affected the city on Monday, there is the problem of how the city handled the protests, as Erin Simpson and Andrew Exum debated on Twitter:
For now I'd like to give Ta-Nehisi Coates, writing for the Atlantic, himself a Baltimore native, the last word:
Now, tonight, I turn on the news and I see politicians calling for young people in Baltimore to remain peaceful and "nonviolent." These well-intended pleas strike me as the right answer to the wrong question. To understand the question, it's worth remembering what, specifically, happened to Freddie Gray. An officer made eye contact with Gray. Gray, for unknown reasons, ran. The officer and his colleagues then detained Gray. They found him in possession of a switchblade. They arrested him while he yelled in pain. And then, within an hour, his spine was mostly severed. A week later, he was dead. What specifically was the crime here? What particular threat did Freddie Gray pose? Why is mere eye contact and then running worthy of detention at the hands of the state? Why is Freddie Gray dead?
The people now calling for nonviolence are not prepared to answer these questions. Many of them are charged with enforcing the very policies that led to Gray's death, and yet they can offer no rational justification for Gray's death and so they appeal for calm. But there was no official appeal for calm when Gray was being arrested. There was no appeal for calm when Jerriel Lyles was assaulted. (“The blow was so heavy. My eyes swelled up. Blood was dripping down my nose and out my eye.”) There was no claim for nonviolence on behalf of Venus Green. (“Bitch, you ain’t no better than any of the other old black bitches I have locked up.”) There was no plea for peace on behalf of Starr Brown. (“They slammed me down on my face,” Brown added, her voice cracking. “The skin was gone on my face.")
When nonviolence is preached as an attempt to evade the repercussions of political brutality, it betrays itself. When nonviolence begins halfway through the war with the aggressor calling time out, it exposes itself as a ruse. When nonviolence is preached by the representatives of the state, while the state doles out heaps of violence to its citizens, it reveals itself to be a con. And none of this can mean that rioting or violence is "correct" or "wise," any more than a forest fire can be "correct" or "wise." Wisdom isn't the point tonight. Disrespect is. In this case, disrespect for the hollow law and failed order that so regularly disrespects the rioters themselves.