Boston Marathon bomber Dzhokhar Tsarnaev offered prosecutors a guilty plea in exchange for life in prison, according to court documents unsealed Wednesday.

Tsarnaev “offered to provide certain kinds of cooperation and assistance, in the course of plea negotiations,” according to the court documents that were examined by NBC News.

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However, prosecutors did not take the deal. Tsarnaev was convicted and sentenced to death for his role in the 2013 bombing that killed three people and injured hundreds more. 

Tsarnaev acted with his brother, Tamerlan, who was killed in a shootout with Boston police officers. 

Prosecutors said in the filing that Dzhokhar Tsarnaev sought to include statements that he had not wanted to kill innocent people. 

The filing also explains why FBI agents rushed to interview the surviving brother in his hospital bed after he was captured.

“Of the two remote-control detonators used during the Marathon bombings, only one was recovered, suggesting that the Tsarnaevs (or someone else) had retained the other one for possible use with additional bombs,” the filing reads.