A story in Mother Jones magazine has teachers and parents explaining how the initial clashes were caused by police in West Baltimore after the funeral of Freddie Gray. Gray, arrested for "running while Black," died with a severed spine after police gave him what police call a "rattle the can" ride in the back of a police van while handcuffed, a practice explained by retired Philadelphia police Captain Ray Lewis. Baltimore police have a long history of abusing and even killing prisoners in this way.
Teachers and parents in West Baltimore say the protests turned violent after police prevented students from going home on buses and public transportation after school and then attacked them. Police had apparently been monitoring social media and read that protesters would be gathering that afternoon at a mall across the street from the school
Keep in mind also that in the wake of other such so-called "riots" it turns out the destruction is never random but is specifically directed at businesses owned by people who live outside the community that have severely exploited the local community. Call it justice, call it vigilante justice, call it what you like, but it's rational and purposeful and not people going berserk or lazy people taking the opportunity get some free stuff, as the media always portrays it.
Any violence directed against Baltimore police will turn out to have been brought upon themselves, as the Mother Jones story makes clear and as has happened before, most recently last summer in Ferguson, MO. Keep in mind too that anything that happens in Baltimore will occur in the context of the ongoing genocide of African Americans by law enforcement nationwide.
Note: The events in Baltimore notwithstanding, as I have noted before, news media coverage of the police is gradually shifting from that of being staunch defenders of police brutality to skepticism and disgust. This local news story from Inkster, MI, that shows officers on video taking time from cleaning blood off themselves to mock their beating victim, a 57-year-old Black man, before taking him to the hospital is another indication of that.
It seems plausible then that news media coverage will eventually begin to put police violence in the context of efforts to suppress the working class and working class discontent, and to place working class reaction to that oppression in the same context.