A transport worker was killed after trying to stop a gunman from shooting commuters in Washington DC on Wednesday morning, authorities said.
Two other people were wounded in the shooting and were treated in hospital for non-life-threatening injuries.
The attack started on a city bus and ended on the platform of a Metro station in south-east Washington, police said.
The suspect was disarmed by bystanders and arrested.
In a statement on Wednesday, the Washington Metropolitan Area Transit Authority said it mourned the loss of a “heroic employee, Robert Cunningham, who intervened on behalf of a customer” at Potomac Avenue Station.
It said Mr Cunningham, 64, worked as a mechanic in the transit authority’s power department and was “a victim of senseless gun violence”.
Maryland Senator Ben Cardin praised him as a “hero” on Thursday, and the mayor of nearby Alexandria also hailed his bravery.
“Mr Cunningham heroically intervened today to protect a customer,” Mayor Justin Wilson said from aboard a city train, adding that it was “a tragic and preventable loss of life”.