Oakland, October 2011: Scott Olsen

Huffington Post, Oakland Police Critically Injure Iraq War Vet During Occupy March

The local police's use of force seriously injured an Occupy activist and Iraq War veteran. Scott Olsen, 24, remains sedated on a respirator, in stable but critical condition at Oakland’s Highland Hospital after being hit in the head with a police projectile. Olsen's roommate, Keith Shannon, 24, told The Huffington Post that Olsen is still in the emergency room.
[...]
Activists staged Tuesday night’s march through downtown Oakland in response to a violent police raid on the Occupy Oakland encampment earlier that day, during which officers rained tear gas and rubber bullets on the activists in an effort to clear the camp. Police arrested scores of protesters during the eviction.

When reached at her Wisconsin home, Sandra Olsen, Scott's mother, told HuffPost that her son's condition was serious. "He has a head injury," she said. "They are still trying to figure it out with him. I don't want to tie up the phone line. He's not in the best shape."

San Jose Mercury News, Marine Scott Olsen injured during Occupy Wall Street confrontation in Oakland

Yahoo/AP: Iraq war vet injured during Oakland protests
(also here: Boston Globe)

Scott Olsen, 24, suffered a fractured skull Tuesday in a march with other protesters toward City Hall, said Dottie Guy, of the Iraq Veterans Against the War. The demonstrators had been making an attempt to re-establish a presence in the area of a disbanded protesters’ camp when they were met by officers in riot gear.

It’s not known exactly what type of object struck Olsen or who might have thrown it, though Guy’s group said it was lodged by officers. Several small skirmishes had broken out in the night with police clearing the area by firing tear gas and protesters throwing rocks and bottles at them.

What hit him? Who knows. Who threw it or launched it? Also unclear. But evidently the protesters definitely threw rocks and bottles. It's plausible that they did, or at least some of them did, but still.