As he planted a backpack containing a bomb near a group of children, Boston Marathon bomber Dzhokhar Tsarnaev made a coldblooded decision aimed at punishing America for its wars in Muslim countries, a federal prosecutor told the jury during closing arguments Monday at Tsarnaev’s death penalty trial.

“This was a cold, calculated terrorist act. This was intentional. It was bloodthirsty. It was to make a point,” Aloke Chakravarty said. “It was to tell America that ‘we will not be terrorized by you anymore. We will terrorize you.’”

Defense attorney Judy Clarke countered by arguing, as she did at the trial’s outset, that Tsarnaev took part in the attack but did so under the malevolent influence of his now-dead older brother, Tamerlan. Clarke repeatedly referred to Dzhokhar Tsarnaev — then 19 — as a “kid” and a “teenager.”

“If not for Tamerlan, it would not have happened,” Clarke said.

The jury is expected to begin deliberating this morning in the case against Tsarnaev, 21, almost two years after the twin bombings near the finish line of the Boston Marathon killed three people and wounded more than 260. It was the nation’s deadliest terror attack since 9/11.

If Tsarnaev is convicted, as expected,the jury will then begin hearing evidence on whether he should get life in prison or a death sentence.

Prosecutors used their closing argument to remind the jury of the horror of that day, showing photographs and video of the carnage and chaos after the shrapnel-packed pressure-cooker bombs exploded. In one video, jurors could hear the agonizing screams of Krystle Campbell, a 29-year-old restaurant manager who bled to death on the sidewalk. Another woman and an 8-year-old boy were also killed.

Taking aim at the argument that Tsarnaev was led astray by his older brother, Chakravarty repeatedly referred to the Tsarnaevs as “a team” and “partners” in the attack.

“That day, they felt they were soldiers. They were the mujahedeen, and they were bringing their battle to Boston,” the prosecutor said.

As for the youngsters killed or maimed by the bomb that was in Dzhokhar Tsarnaev’s backpack, Chakravarty said: “These children weren’t innocent to him. They were American. Of all the places that he could have placed the bomb, he placed it right there.”

Tamerlan Tsarnaev, 26, died four days after the bombings after a shootout with police.

Clarke struck a conciliatory tone in her closing argument, admitting the attack brought “tragedy, suffering and grief in dimensions that none of us could imagine were possible.”

But in a strategy clearly aimed at saving her client from the death penalty, Clarke said Tamerlan Tsarnaev played a much more prominent role, planning the attacks, buying bomb components and researching how to build the devices. And his fingerprints — but not his brother’s — were found on pieces of the two bombs, she said.

“We’re not asking you to excuse the conduct,” Clarke said, “but let’s look at the varying roles.”