Occupy San Francisco's "Day of Action" turned violent Friday night when protesters occupied an abandoned hotel and began throwing objects at police officers from the roof, police said.

"Once they gained access [to the hotel], some of them made it to the top of the roof and they then began to throw bibles down at the officers," San Francisco Police Department spokesman Carlos Manfredi said.

"One of officers was struck with a brick to the chest and one of our lieutenants was struck in the hand with an object and may have damaged or even broken his hand," he said.

Protesters began the day Friday by targeting San Francisco's financial institutions like the Federal Reserve, Fannie Mae, Wells Fargo, Bank of America, the SEC, Citibank, Chase, and Bechtel.

"The banks are not being responsible and we are tired of being foreclosed, getting in so much debt; it's just time to change the system," protester Wendy Kaufmyn told ABC News station KGO-TV in San Francisco.

Protesters began chaining themselves to the entrances of Wells Fargo Bank's corporate headquarters in downtown San Francisco.

Police in riot gear were called in, and 18 protesters were arrested. That did not stop others from trying to block a nearby Bank of America branch.

Among the protesters was Scott Olsen, the Iraq War veteran who was injured during an Occupy Oakland protest in October, when he was struck in the head by a blunt object other protesters said was a tear gas canister shot by police.

Across the country, protesters also rallied at courthouses Friday to challenge a 2010 Supreme Court decision that largely removed limits on union and corporate spending in support of political campaigns.

Protesters descended on the U. S. Supreme Court in Washington D.C. as part of the nationwide effort that Occupy Wall Street has dubbed "Occupy the Courts."