Feb. 4 (UPI) -- Federal prosecutors have charged the Chicago man accused of gunning down two Israeli Embassy staffers in Washington, D.C., in May with terrorism-related offenses, the Justice Department announced Thursday.

A 13-count superseding indictment unsealed Wednesday charges Elisa Rodriguez, 31, with four counts of acts of terrorism while armed, along with a federal statutory aggravating factor alleging he planned the attack as an act of terrorism.

Rodriguez was already facing several charges, including first-degree murder counts in the May 21 shooting deaths of Yaron Lischinsky, 30, and Sarah Lynn Milgrim, 26.

The couple, who were reportedly about to become engaged, were attending an event at the Capital Jewish Museum when they were shot and killed outside the facility.

Related