The Justice Department announced Tuesday it will not file federal civil rights charges against George Zimmerman, the Florida man who was acquitted last year of second-degree murder for shooting Trayvon Martin, an unarmed black teenager. 

“Though a comprehensive investigation found that the high standard for a federal hate crime prosecution cannot be met under the circumstances here, this young man’s premature death necessitates that we continue the dialogue and be unafraid of confronting the issues and tensions his passing brought to the surface,” Attorney General Eric Holder said in written statement. “We, as a nation, must take concrete steps to ensure that such incidents do not occur in the future.”

Thursday marks the third anniversary of Martin’s death. 

“Although we are disappointed in these findings, it has steeled our resolve to continue traveling the country with the message of the Trayvon Martin Foundation which is dedicated to protecting our youth and empowering those who demand justice and peace,” Martin’s family said in a statement following the DOJ announcement.

The decision, announced in the waning days of Holder's tenure, resolves a case that focused on self-defense gun laws and became a flashpoint in the national conversation about race two years before the Ferguson, Missouri, police shooting. 

Zimmerman has said he acted in self-defense when he shot the 17-year-old Martin during a confrontation inside a gated community in Sanford, Florida, just outside Orlando. Martin, who was black, was unarmed when he was killed. 

Once Zimmerman was acquitted of second-degree murder by a state jury in July 2013, Martin's family turned to the federal investigation in hopes that he would be held accountable for the shooting. 

That probe focused on whether the killing amounted to a federal civil rights violation, which would have required proof that it was motivated by racial animosity. Although Martin's parents have said Zimmerman initiated the fight and racially profiled Martin, the Justice Department said there was not enough evidence to bring federal civil rights charges, which would have required proof that the killing was motivated by racial animosity.

"Although the department has determined that this matter cannot be prosecuted federally, it is important to remember that this incident resulted in the tragic loss of a teenager's life," Acting Assistant Attorney General Vanita Gupta of the Civil Rights Division said in a statement.  "Our decision not to pursue federal charges does not condone the shooting that resulted in the death of Trayvon Martin and is based solely on the high legal standard applicable to these cases." 

Zimmerman did not testify at his trial, but he told investigators that he feared for his life as Martin straddled him and punched him during the fight. 

Fox News' Jake Gibson and The Associated Press contributed to this report.