A former white supremacist convicted of murdering a family of three was executed Tuesday morning -- the first federal execution since 2003 and part of a new wave of such executions by the Department of Justice.

Daniel Lewis Lee was executed by lethal injection on Tuesday morning, after the Supreme Court reversed a lower court decision blocking the execution on Monday.

BARR ORDERS EXECUTION DATES FOR FOUR CONVINCTED CHILD MURDERERS AFTER TWO-DECADE HIATUS

In a 5-4 decision, the court’s conservatives ruled that the execution could “proceed as planned.”

Lee was convicted of the murders of William Mueller, his wife, Nancy, and her 8-year-old daughter, Sarah Powell, as part of an attempted robbery to fund a white supremacist group. After robbing and shooting them with a stun gun, he covered their heads with plastic bags, sealed them with duct tape and threw them into a bayou.

The execution had faced opposition from anti-death penalty advocates, but also pushback from the family of the victims, who had argued for a delay because of the coronavirus pandemic making it risky for them to attend in person. They had also called on President Trump to commute Lee's sentence to life in prison.

SUPREME COURT CLEARS WAY FOR EXECUTION OF FEDERAL PRISONER 

Lee’s execution is one in a new wave of federal executions, breaking an informal moratorium on the practice in place since 2003. Attorney General William Barr last month ordered the scheduling of four executions for prisoners convicted for horrific crimes.

“The American people, acting through Congress and Presidents of both political parties, have long instructed that defendants convicted of the most heinous crimes should be subject to a sentence of death,” Barr said in a statement.

Barr had initially scheduled executions last year after an Obama-era review of capital punishment was completed, but a district court had issued an injunction preventing the Bureau of Prisons from carrying them out. The U.S. Court of Appeals vacated that injunction in April.

The other inmates scheduled for execution are:

Wesley Ira Purkey, who was convicted or raping and murdering a 16-year-old, and murdered an 80-year-old woman with a claw hammer;

Keith Dwayne Nelson, who kidnapped a 10-year-old girl rollerblading in front of her home, and raped and strangled her to death with a wire;

Dustin Lee Honken, who shot and killed five people -- including a mother and her 10- and 6-year-old daughters.

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Honken is scheduled to be executed on Friday, Purkey’s execution is on hold as part of a legal claim, and Nelson is scheduled to be executed in August.

The Associated Press contributed to this report.