FBI via Reuters file Boston Marathon Bombing suspect Dzhokhar Tsarnaev, 19, is pictured in this undated FBI handout photo.

Boston bombing suspect Dzhokhar Tsarnaev wrote anti-American messages while hiding from police in a boat and had downloaded instructions on making bombs from an al-Qaeda magazine around the time of the attack, a grand jury indictment charged Thursday.

Prosecutors release details in the indictment against Boston Marathon bombing suspect Dzhokhar Tsarnaev.

The 30-count indictment includes charges of using weapons of mass destruction and killing four people, federal prosecutors announced more than two months since the attacks.

Tsarnaev, 19, has been accused of setting off bombs near the finish line of the city's annual race on April 15 with the help of his brother Tamerlan. The blasts killed three people, and investigators believe the brothers killed a university police officer in the days after the attack while attempting to evade capture.

The indictment alleges that the two brothers used improvised explosive devices made from pressure cookers, explosive powder and shrapnel that “were designed to shred skin, shatter bone, and cause extreme pain and suffering, as well as death,” according to the rand jury indictment.

While hiding from police in a boat in the backyard of a Watertown, Mass., home, Tsarnaev scrawled anti-American messages that gave investigators some insights into why the teen allegedly carried out the attack.

"The U.S. Government is killing our innocent civilians," "I can't stand to see such evil go unpunished," and "We Muslims are one body you hurt one you hurt us all" were some of the messages he scribbled while lying in the boat wounded.

At a press conference Thursday, officials declined to comment on whether they viewed the notes as a confession.

United States Attorney Carmen M. Ortiz also would not specifically describe the motive behind the brothers’ attacks, but said the indictment indicates they were protesting American foreign policy.

NBC's Pete Williams has the latest on the 30 counts Boston bombing suspect Dzhokhar Tsarnaev has been charged with.

The document shows Tsarnaev frequently used the Internet to read radical Islamic publications that often advocated for violence. An issue of al-Qaeda’s Inspire magazine found on his computer had instructions for building explosives using pressure cookers, according to the charges.

He also downloaded a publication called “Defense of the Muslim Lands, the First Obligation After Imam,” which “advocates violence designed to terrorize the perceived enemies of Islam,” according to the indictment.

Seventeen of the charges carry a maximum sentence of life in prison or death. Ortiz said it will be up to Attorney General Eric Holder whether prosecutors will seek the death penalty.

Tsarnaev was severely injured after a gun battle with police and has been held in a Massachusetts prison hospital after his April 19 capture. His brother Tamerlan was killed in the course of the manhunt.

Though the brothers have lived in in the United States for about 10 years, they hail from Dagestan, a turbulent region that has become a hotbed for Islamic extremism. In early 2012, Tamerlan Tsarnaev traveled to the region, a move that prompted Russia to alert U.S. authorities of possible terrorist activities. An FBI investigation at the time was inconclusive.

FBI interviewed the man but found no signs that he had been radicalized.

The indictment gives a detailed account of many known facts about the attack the Tsarnaevs, but also includes some details about how they prepared for bombing.

In February, Tamerlan Tsarnaev traveled to New Hampshire where he purchased 48 mortars explosive powder from a fireworks store.

The two also went to a Manchester, N.H., gun range for practice in late March where they rented 9mm handguns, the indictment states.

Tsarnaev is scheduled to be arraigned July 10 in Boston.

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