From Olsen's Facebook fan page http://www.facebook.com/pages/Scott-Olsen/191248674286220?sk=wall OAKLAND, Calif. (AP) — The Iraq War veteran injured in clashes between police and anti-Wall Street protesters felt so strongly about economic inequality that he wanted to do something to change it, his roommate said Thursday.

Scott Olsen, 24, joined the protests as he worked his day job as a network engineer and left his apartment each night to sleep alongside protesters in San Francisco and Oakland, Calif., Keith Shannon said.

Olsen apparently suffered a fractured skull Tuesday during the clashes.

It's not known exactly what type of object struck Olsen or who might have thrown it. The group Iraq Veterans Against the War said officers were responsible for his injury.

Oakland Police Chief Howard Jordan said officials will investigate whether officers used excessive force.

Olsen's has become a rallying cry, with demonstrators in New York City marching on Wednesday night in support of their counterparts in Oakland and a movement website declaring: "We are all Scott Olsen."

Another round of vigils was being organized Thursday.

Olsen, who is originally from Wisconsin, served two tours of duty in Iraq, makes a good living at a San Francisco software company and had a hillside apartment that overlooks San Francisco Bay.

And yet, Shannon said, Olsen felt strongly about the wealth disparity between the rich and everyone else.

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

Shannon said his roommate felt the anti-Wall Street movement had a chance to create real change.

So each night, he would go out to the tent camps that have sprung up over the past month in cities as the movement spread to protest economic inequality and what they see as corporate greed.

Shannon said Olsen usually called with his whereabouts.

On Tuesday night, Olsen had planned to be in San Francisco, but changed course after his veteran's group decided to go to Oakland to support the protesters there after police cleared an encampment outside city hall.

"I think it was a last minute thing," he said. "He didn't think about it."

Joshua Shepherd, 27, a Navy veteran who was standing nearby when Olsen got struck, said he didn't know what hit him. "It was like a war zone," he said.

Then there was a scramble and he couldn't clearly see the rush of folks who went to Olsen's aid.

A video posted on YouTube showed Olsen being carried by other protesters through the tear gas, his face bloodied. People shout at him: "What's your name? What's your name?" Olsen, however, just stares back.

Shepherd said it's a cruel irony that Olsen is fighting for his life in the country that he fought to protect.

"He was over there protecting the rights and freedoms of America and he comes home, exercises his "freedoms" and, it's here, where he's nearly fatally wounded," Shepherd said.

A hospital spokesman said Olsen was upgraded to fair condition and moved into an intensive care unit on Thursday. His uncle said his parents were flying in from Wisconsin to be with him.

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

People at OPSWAT, the company where Olsen works, were devastated after learning of his injuries. They described him as a humble, quiet guy who worked hard over long hours.

"He's been a big piece of what we do here and our growth strategy, so obviously it's pretty devastating for us that he's in the shape he's in," said Jeff Garon, the company's director of marketing.

Olsen was awarded seven medals while serving in the U.S. Marine Corps, which he left as a lance corporal in November 2009 after serving for four years.

He went on two tours in Iraq, one in 2006-2007 and another in 2008, where he worked as a data network specialist. He was awarded seven medals, including the Navy-Marine Corps Achievement Medal, according to the Marine Corps.

Olsen moved to the Bay Area in July, and quickly found friends in the veterans against the war group.

The lanky man with a dry sense of humor and sarcastic wit did not show a lot of interest in politics as a teen — he has two tattoos for the group "Insane Clown Posse" on his upper arms, Shannon said.

His tours of duty in Iraq made him more serious, Shannon said.

"He wasn't active in politics before he went in the military, but he became active once he was out ... the experience in the military definitely shaped him," Shannon said.

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Associated Press writers Dinesh Ramde in Milwaukee, Garance Burke in San Francisco and Julie Watson in San Diego contributed to this report. Dearen reported from San Francisco.