(CNN) -- Federal prosecutors will seek the death penalty against Boston Marathon bombing suspect Dzhokar 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 Boston Marathon, 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.
Dzhokar Tsarnaev is charged with 30 federal counts stemming from the attack. He has pleaded not guilty to all charges.