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: