(CNN) -- Federal prosecutors will seek the death penalty against Boston Marathon bombing suspect Dzhokhar Tsarnaev, U.S. Attorney General Eric Holder said Thursday afternoon.
Authorities allege Tsarnaev, a Chechnya-born American, and his brother Tamerlan planted two homemade bombs near the finish line of the April 15 race, killing three and injuring more than 250.
A Massachusetts Institute of Technology police officer was killed three days later, triggering the massive manhunt that led to Tsarnaev's capture. His brother was shot and killed by police during the manhunt.
"The nature of the conduct at issue and the resultant harm compel this decision," Holder said in a statement released by the Justice Department.
After Holder made his decision, prosecutors filed Thursday a notice with a federal court that they would seek the death penalty in the case, according to Carmen Ortiz, the U.S. attorney for Massachusetts.
Dzhokhar Tsarnaev is charged with 30 federal counts stemming from the attack. He has pleaded not guilty to all charges.
Since taking office, Holder has sought the death penalty in dozens of cases, but at lower rate than his recent predecessors, officials and death-penalty watchers say.
Despite Holder's decision to authorize the death penalty in the Tsarnaev case, prosecutors still could reach an agreement with his attorneys, who include death penalty lawyer Judy Clarke, to plead guilty and receive life in prison or another sentence.
Holder issued a memo in 2011 that forbids using the death penalty threat to obtain guilty pleas. But that doesn't prohibit plea deals coming after the attorney general's recommendation.
Federal officials weighed a number of factors before they announced their decision, including the opinions of victims of the deadly attack.
Survivors were asked to fill out a questionnaire about what they thought about the death penalty.
Reached before federal authorities announced their decision to seek the death penalty, Zubeidat Tsarnaev, the suspect's mother, did not comment on the specifics of the case.
"The only thing I want to say is, I want the whole world to hear that I love my son, my precious Dzhokhar. That's it," she told CNN's Nick Paton Walsh.
-- CNN's Evan Perez and Susan Candiotti contributed to this report.