The U.S. Secret Service has brought in the FBI for an investigation into a shooting that occurred near the White House Friday, as law enforcement discover multiple bullets at the scene and the primary suspect remains on the loose. 

According to a Secret Service statement Thursday, law enforcement found a bullet that smashed a window at the White House before being stopped by a second layer of "ballistic glass." Another round was found outside the White House. The Secret Service said the damage "has not been conclusively connected" to the shooting. 

Fox News has learned that the FBI joined the investigation on Wednesday at the request of the Secret Service and U.S. Park Police. The FBI has extensive expertise in evidence gathering, which could explain why the agency was called in to assist. 

Law enforcement continue to search for the suspect, 21-year-old Oscar Ortega-Hernandez. The suspect has a record of arrests in Idaho, Utah and Texas, according to MyFoxDC, and reportedly is believed to be mentally ill. 

Park Police originally obtained an arrest warrant for Ortega-Hernandez after discovering an AK-47-style rifle in an abandoned car Friday night. The car was found after Secret Service officers heard shots being fired between two vehicles about a half-mile from the White House. 

U.S. Park Police spokesman Sgt. David Schlosser said Sunday that officers had obtained an arrest warrant for the suspect on a felony charge of carrying a dangerous weapon, in connection with the incident. 

Ortega-Hernandez is thought to have remained in the Washington, D.C., area following Friday's drama. Secret Service describe him as a 21-year old, Hispanic male, 5'11", 160 pounds, with a medium build, brown eyes and black hair.

President Obama and First Lady Michelle Obama were in California at the time of the shooting, before traveling to Hawaii for the Asia-Pacific Economic Cooperation forum. 

News of the bullets' discovery broke shortly after the president landed in Australia for a brief 27-hour visit.