WASHINGTON (AP) — A man "randomly" brandishing a firearm shot three people, killing one, in a Wednesday morning rampage in the nation's capital that started on a city bus and ended in a Metro tunnel after passengers attacked and disarmed him.

Authorities were still piecing together the chaotic series of events that left two people with gunshot wounds to the leg and a Metro employee shot dead. The shooter is in police custody and has not been publicly identified.

Metropolitan Police Department Executive Assistant Chief Ashan Benedict praised the "heroic actions of our citizens, our community, to disarm this shooter."

But he added, "The fact that our citizens had to intervene with armed gunmen is disturbing to me."

The violence began shortly after 9 a.m. when the man began brandishing a weapon and confronting passengers on a city bus in the southeast area of the city. The man pursued one of the passengers off the bus and shot them in the leg, Benedict said.

The man then went down the escalator of the nearby Potomac Avenue Metro stop, confronted someone who was buying a Metro pass and shot that person in the leg as well. Both victims were recovering in local hospitals.

The armed man then went down to the train platform and began confronting a woman there. Benedict characterized his behavior as deeply erratic, saying, "He's walking around brandishing a firearm and just randomly engaging people in confrontation. He's clearly agitated about something."

A Metro employee tried to intervene and was killed by a gunshot. The identity of the slain transit worker has not been released, but Benedict said their "heroism had to be recognized."

The man then attempted to board a Metro train and was apparently confronted and disarmed by the passengers. He exited the train car and was taken into custody by police officers, who recovered his weapon on the train tracks, Benedict said.

Mayor Muriel Bowser said the shootings highlight the need for serious gun control. Bowser and the Police Department have recently endured intense public pressure after a city employee shot and killed a 13-year old boy who was part of a group of youth breaking into parked cars on his block. The resident was charged this week with second-degree murder.

"We're focused on how we get guns out of our city," Bowser said. "Whether it's the Metro, it's the street, it's in individual homes, we know that we have guns that are creating tragedies in our city and in our nation."

Metro General Manager Randy Clarke said his administration had recently beefed up security measures, including increased police patrols and video surveillance. But he said the morning's incident was indicative of a wider issue beyond Metro security.

"This is not a Metro-specific safety issue; it's an American gun violence issue," Clarke said.