If I may ask, what's on these pictures? Is it the undercover cop that held people at gunpoint?
Armed undercover cops were hiding out (civilian clothes, bandanas covering their faces) in a protest in Oakland. When someone in the crowd recognized what they were and outed them (one person admits to pulling off their bandana), they started shoving their way through the crowd to get away. Someone shoved back (probably not realizing they were cops since they were still in civilian clothes and had not identified themselves) and their response was to tackle him to the ground and put him in handcuffs.
When people started to gather nearby to protest the the police brutality happening right in the middle of their police brutality protest, one of the officers drew his baton and firearm and waved it at the crowd and photographer.
Story here:
http://www.ktvu.com/story/27606016/undercover-cop-pulls-gun-on-demonstrators
Edit: I have not seen any reliable news source reporting that either officer was "punched and kicked", only that one of the officers was 'pushed to the ground'. Given that the protestors had broken into an auditorium to disrupt a speech (ironically, about peaceful protests having an effect) and supposedly smashed a store front and an ATM, it's not outside the realm of possibility though and honestly nobody looks good in the whole affair.
That said, armed undercover cops wearing masks lurking in the middle of a protest sounds like the perfect recipe for someone to get shot.
Edit 2: They were apparently attempting to incite the protestors to violence too. That at least gives us a reason as to how the protesters were able to figure out they were cops;
According to them, as the marches proceeded through Berkeley and Oakland, the two masked officers banged on windows and attempted to devolve protests into looting and rioting. (
source)
Here's the GAF thread on it;
http://www.neogaf.com/forum/showthread.php?t=950296