A federal grand jury Thursday returned a 30-count indictment against Dzhokhar Tsarnaev, the suspect in the April 15 Boston Marathon bombings, providing new detail about his interest in radical Islamist literature and describing for the first time messages he scrawled inside a dry-docked boat just before his capture.

“The U.S. Government is killing our innocent civilians,” Tsarnaev wrote on the walls and beams of the boat, which was in a back yard outside a police cordon he had slipped through in Watertown, Mass.

He also wrote: “I can’t stand to see such evil go unpunished.”

Tsarnaev, a naturalized U.S. citizen, was charged with the use of a weapon of mass destruction resulting in death; the bombing of a public place that resulted in death; and the murder of a Massachusetts Institute of Technology police officer, among other crimes.

Seventeen of the charges carry the death penalty or life in prison, the U.S. attorney’s office in Boston said. The Justice Department will have to decide whether to pursue a capital prosecution, a decision that ultimately rests with Attorney General Eric H. Holder Jr., according to Carmen Ortiz, the U.S. attorney in Boston.

“I do want to say that I have met several of those that were injured on April 15th as well as members of the deceased families,” Ortiz said Thursday at a news conference in Boston. “Their strength is extraordinary, and we will do everything that we can to pursue justice not only on their behalf, but on behalf of all of us.”

Tsarnaev, who was hospitalized with a throat wound after his arrest, is scheduled to be arraigned July 10 in federal court in Boston.

The indictment describes how Tsarnaev, 19, and his older brother, Tamerlan, who was killed after a shootout with police April 19, allegedly moved toward the finish line at the Boston Marathon, carrying improvised bombs in black backpacks.

At 2:40 p.m. Tamerlan, 26, walked to the front of Marathon Sports on Boylston Street as his brother moved to a position in front of the Forum restaurant, according to the indictment. The bombs were placed by low metal barriers along the edge of the street where hundreds of spectators were watching the runners.

At 2:48 p.m. Tsarnaev called his older brother on a cellphone; they communicated for just a few seconds, the indictment says. Seconds later, Tamerlan detonated the first bomb, killing Krystle Marie Campbell, a 29-year-old native of Medford, Mass., who was cheering on her boyfriend. After a few more seconds, Tsarnaev detonated the second device, killing 7-year-old Martin Richard, who was attending the event with his family, and Lingzi Lu, a 23-year-old Chinese citizen and graduate student at Boston University.

More than 260 people were injured in the blasts, many of them seriously. More than a dozen amputations were performed in area hospitals.

Preparations for the bombings began at least as early as Feb. 6, when Tamerlan purchased 48 mortars containing eight pounds of low-explosive powder at a fireworks store in Seabrook, N.H., according to the indictment.

In March, the ethnic Chechen brothers traveled to a shooting range in Manchester, N.H., rented two 9mm handguns, bought 200 rounds of ammunition and practiced shooting for an hour.

The instructions for the bombs — made of pressure cookers, low-explosive powder and shrapnel — were downloaded by Tsarnaev from the magazine Inspire, an English-language publication produced by al-Qaeda’s Yemeni affiliate, the indictment alleges.

The indictment says Tsarnaev had downloaded a number of radical publications, including a digital copy of a book titled “The Slicing Sword,” which calls on Muslims not to offer allegiance to governments that “invade Muslim lands.” A foreword to the book was written by Anwar al-Awlaki, the American-born propagandist for al-Qaeda’s Yemeni affiliate who was killed in a joint CIA-military drone operation in Yemen in September 2011.

Tsarnaev also downloaded publications such as “Defense of the Muslim Lands” and “Jihad and the Effects of Intention Upon It,” the indictment says.

The indictment suggests that the brothers were self­radicalized by way of the Internet. There is no mention of a wider conspiracy or of direct contact with a terrorist organization. After the bombings, U.S. investigators traveled to Russia to see whether Tamerlan had formed any kind of alliance with radicals there during a six-month stay in the Russian republic of Dagestan in 2012.

Tsarnaev and his brother were identified as suspects from video footage that the FBI and other law enforcement agencies searched through after the attacks and released to the public in order to get the bombers’ names.

On April 18, the night their pictures were released, Tsarnaev and his brother armed themselves with five bombs, a 9mm semiautomatic handgun, ammunition, a machete and a hunting knife, according to the indictment.

At 10:25 p.m. they shot and killed Sean Collier, an MIT police officers, in an unsuccessful attempt to get his weapon, the indictment says. Then they carjacked a Mercedes SUV, but the driver escaped early the next morning.

About 12:50 a.m April 19, the brothers shot at and threw bombs at Watertown police officers. Tamerlan, who was shot, was tackled by three officers who attempted to handcuff him. Tsarnaev then drove the Mercedes at the group of officers and ran over his brother, “seriously injuring him and contributing to his death,” the indictment says.

Tsarnaev drove off and quickly ditched the Mercedes. He smashed his cellphones and found his way to the boat. Police eventually surrounded the boat, and Tsarnaev, who was by then unarmed, survived a volley of gunfire into the vessel before he was apprehended.

Julie Tate contributed to this report.