1 of 2 | Secret Service officers respond following reports of gunfire near the White House in Washington, D.C., on Saturday. Photo by Aaron Schwartz/UPI | License Photo

May 24 (UPI) -- The gunman who opened fire at the White House this weekend before being fatally shot by Secret Service officers has been identified as Nasire Best, unnamed sources confirmed to multiple media outlets.

The 21-year-old had previous encounters with the Secret Service and had previously posted threatening statements online, the sources told CBS News, NBC News and CNN. The sources said Best had never acted violently or brandished a weapon prior to Saturday evening, when police said he approached a checkpoint at the White House, pulled a firearm from his bag and opened fire.

Officers returned fire, striking Best, who was transported to a hospital where he was declared dead, Anthony Guglielmi, chief of communications for the Secret Service, said in the statement.

A bystander was also injured in the shooting and was in critical condition.