-Security officials recently started scaling back fencing around U.S. Capitol. Robert Contee, the acting D.C. police chief, said the incident "does not appear to be terrorism-related" and that there was no indication of a "nexus to a member of Congress".
The officials say the suspect was critically wounded and was taken into custody.
Evans is the seventh Capitol Police member to die in the line of duty in the department's history, according to the Officer Down Memorial Page, which tracks deaths of law enforcement. Both officers are injured.
The U.S. Capitol was placed under lockdown amid what Capitol Police described as "an external security threat".
Since then security officials have said there is an ongoing threat from extreme-right groups and some Trump supporters.
Journalist Jake Sherman posted footage of a helicopter landing on the east front of the Capitol complex.
The FBI's Washington Field Office is responding to the situation and is now providing support to the Capitol Police. National Guard troops who have guarded the building since then were seen mobilizing around the area of the incident.
In early March, the House recessed early after Capitol Police said it had discovered evidence of a "possible plot" against legislators tied to the same far-right conspiracy theorists who helped spark the January 6 violence.
The blocks surrounding the Capitol building were once again surrounded by law enforcement as the area was secured.
Temporary fencing that had been erected around the Capitol's outer perimeter was removed late last month, though temporary fencing remains in place closer to the building.
But Congress is now in recess, meaning the majority of politicians are not at the Capitol complex today. "The process of lowering the flags may take longer than usual because of the Capitol's current lockdown status", said Drew Hammill, Pelosi's deputy chief of staff.