Angie Craig, a Minnesota Democrat, fought back by throwing hot coffee at the assailant, a police report says. Kendrick Hamlin is accused of punching her and grabbing her neck.
The 26-year-old, of no fixed address, has been charged with simple assault. The case is not thought to be politically motivated.
She called 911 emergency services and the “assailant fled the scene”. He said Ms Craig thanked DC Metropolitan Police Department “for their quick response and asks for privacy at this time”.
According to a public incident report from the Metropolitan Police Department, Ms Craig told investigators that there was a person acting erratically and possibly under the influence of drugs in the lobby of her apartment building in the busy H Street area near Capitol Hill.
When she boarded the lift, the person followed her inside and “began to randomly do push-ups” after she bade him good morning, says the report.
The person allegedly punched Ms Craig in the chin and grabbed her neck. She reportedly defended herself by throwing hot coffee at the attacker. Police had earlier released a photo of the suspect and asked the public for help identifying him.
House of Representatives Democratic leader Hakeem Jeffries said the caucus was “horrified” by the attack.
US Senator Amy Klobuchar tweeted: “To give you a sense of how strong Angie is, she went straight to the Hill this morning and attended a meeting… no one messes with Angie.”
Ms Craig serves Minnesota’s second district, an area south of the city of St Paul. Last year Congress approved funding to beef up security for lawmakers, who receive thousands of threats every year.
By, Maxmiller Kerubo