WASHINGTON — The Justice Department said Thursday that it would seek the death penalty against Dzhokhar Tsarnaev, the man accused of killing and maiming people with homemade bombs at the Boston Marathon finish line last year.

The decision sets in motion the highest-profile federal death penalty case since Timothy J. McVeigh was prosecuted and executed for the 1995 bombing of the Alfred P. Murrah Federal Building in Oklahoma City.

“Dzhokhar Tsarnaev targeted the Boston Marathon, an iconic event that draws large crowds of men, women and children to its final stretch, making it especially susceptible to the act and effects of terrorism,” prosecutors wrote in an eight-page document filed in federal court in Boston.

They said Mr. Tsarnaev showed no remorse for the attack. They also cited the age of one of the victims, 8-year-old Martin Richard, in arguing that the death penalty was warranted.