Baltimore police officer throws rock at protesters during riots

In the image above, a Baltimore police officer is seen hurling a rock at protestors.

There is no context attached to it, but is that a regulation rock, officer?

Following the hospitalisation of several officers yesterday, Baltimore police Capt. Eric Kowalczyk said: "You're gonna see tear gas, you're gonna see pepper balls," but there was no mention of projectiles forming part of its riot-dispersing techniques.

A video has also emerged showing other police trading rock/concrete/brick projectiles with rioters, in a juvenile yet deadly game of back-and-forth:

Buildings have been looted and burned in the riots, which were precipitated by the funeral of Freddie Gray, a black man who died from spinal injuries while in police custody, though the vast majority of the protests have been peaceful.