OAKLAND, Calif. -- The Iraq War veteran injured during a clash between police and anti-Wall Street protesters wasn't taking part in the demonstrations out of economic want.

Scott Olsen, 24, makes a good living at a software company and rents a hillside apartment with views of San Francisco Bay. And yet, his friends say, he felt so strongly about economic inequality in the country that he fought for that he slept at a San Francisco protest camp after work.

"He felt you shouldn't wait until something is affecting you to get out and do something about it," said friend and roommate Keith Shannon, who served with Olsen in Iraq.

It was that feeling that drew him to Oakland on Tuesday night, when the clashes broke out and Olsen was struck by a projectile that fractured his skull. Police say they responded only when protesters began throwing bottles and other items at them.

Now, even as officials investigate exactly where the projectile came from, and from whom, Olsen has become a rallying cry for the Occupy Wall Street demonstrators across the nation, with Twitter users and protest websites declaring: "We are all Scott Olsen."

In Las Vegas, a few dozen protesters held a vigil Wednesday night, carrying glow sticks and projecting a photo of the Marine in uniform onto the corrugated-metal side of building at their camp. More vigils were being planned Thursday night in other cities.

Elsewhere, officials took steps to close some camps that sprang up since the movement began last month against what protesters see as corporate greed and a government that caters to the wealthiest and big business. In Nashville, Tenn., officials imposed a curfew for a camp at the Capitol complex. In Providence, R.I., officials notified protesters that they were violating laws prohibiting camping overnight at a park.

On Thursday, however, most of the talk was of Olsen and who was responsible for his injury. The group Iraq Veterans Against the War blamed police. Police say they used tear gas and bean-bag rounds, not flash grenades and rubber bullets as some demonstrators have charged.

Interim Oakland police Chief Howard Jordan said Wednesday that the charges of excessive use of force are being investigated.

Olsen's condition improved on Thursday, with doctors transferring him from the emergency room to an intensive care unit. Shannon said Olsen is scheduled for surgery to relieve pressure from brain swelling. His parents were flying to Oakland from Wisconsin, his uncle said.

"His mother, this is obviously a heartbreaker to her," said George Nygaard, also a Marine veteran, said. "I don't think she understands why he was doing this."