A 21-year-old man was shot and killed by U.S. Secret Service agents near the White House on Sunday evening after he began shooting at a security checkpoint. The man, named Nasire Best from Maryland, pulled out a pistol and fired at a security booth, but was stopped by agents. The President was inside the White House at the time, but was not harmed.

A bystander was also hit by gunfire during the event and is in critical condition at hospital. Officers were not injured. Police have said the suspect had mental illness and was known to authorities.

The city has seen two other shootings near important locations in the past month. Law enforcement is now investigating the man’s motives and how he got the gun. The White House was locked down for a short time, and the nearby street stayed closed while police collected evidence.