A Lakewood, Colorado, police officer was killed and three other officers were wounded Thursday evening after a man opened fire during an encounter on a public bus, police said. Officers returned fire and killed the man. A bystander was also injured, though police did not immediately say how that person was hurt.

The encounter began around 6:30 p.m. local time on November 5, when officers responded to a report of a suspicious person near West Colfax Avenue and Wadsworth Boulevard, about five miles west of downtown Denver. Police spokesperson John Romero told reporters the man was trying to board a bus and opened fire within seconds of the officers approaching, according to ABC News.

The Regional Transportation District confirmed that the shooting occurred aboard a bus operating Route 76 under contract for the agency. A team that investigates police uses of deadly force in Jefferson County will review the shooting, the department said. That review will come after a first night in which authorities could describe the basic encounter but had yet to identify those involved or explain how the civilian was injured.

What police said about the encounter

In its initial account, the city said officers made contact with the man aboard the northbound bus. Police believed he may have been involved in a hit-and-run earlier Thursday, a possible connection Romero described at the briefing. Authorities had yet to explain what evidence linked him to that earlier incident, and the reason for the initial call should be distinguished from the sequence that led to the exchange of gunfire.

All four officers were taken to hospitals, and one died of their injuries. The city said the three surviving officers were in stable condition after describing the injuries among the four officers as serious to critical. The Associated Press reported that police had not released the names of the officers or the man. The bystander’s injury was reported separately from the gunshot wounds to the officers; police did not immediately describe its cause or severity.

The bus operator’s response

The transit agency said its personnel responded immediately and were cooperating with Lakewood police. In a Thursday statement, the agency reported no continuing impact on its service as of 9:02 p.m. local time. Local reporting said another bus picked up passengers from the vehicle involved. Those accounts describe two points in the response: the immediate need to move passengers from the scene and the status of the transit network later in the evening.

The police asked people to avoid the area as investigators worked at the intersection. KRDO, citing information from Gov. Jared Polis and local reporting partners, said the Colorado State Patrol was assisting at the scene and the Colorado Bureau of Investigation was supporting the investigation. The governor offered condolences to the officer’s family and said the wounded officers and the civilian were receiving care. Transit officials also acknowledged the effect on passengers, the bus driver and the staff who responded.

For context, the agency’s security figures show 2,319 calls for service across the system in September, down from 2,743 a year earlier. Its dispatch totals include reports ranging from unattended bags to suspected drug activity, and the agency tracks criminal incident reports separately. Neither figure isolates gun violence or tells riders how often comparable incidents occur on Route 76. Thursday’s shooting began with a local police response, according to authorities, and the transit agency’s role in the investigation is to cooperate with the police handling the case.

Who will investigate the use of force

Lakewood police said the First Judicial District Critical Incident Response Team will investigate. The district attorney’s office describes it as a group of investigators from multiple jurisdictions that reviews cases in which officers use deadly force in Jefferson or Gilpin counties. The team presents the completed investigation to the district attorney, who reviews the evidence and decides whether to file charges against an officer. If prosecutors decide against charges, the office says it makes a letter explaining its decision available to the public.

That process is separate from the preliminary chronology Lakewood police gave at the scene. The district’s published protocol calls for critical incident scenes to be treated as crime scenes and for investigators to record eyewitness interviews when possible. In Lakewood, the inquiry will have to account for a fast encounter around an occupied public vehicle as well as the actions of the officers who returned fire. The fact that a review is underway does not establish what it will find.

What remains unknown

Police said they expected to release more information Friday after reviewing incoming material. Among the unresolved questions are how the bystander was injured and how firmly investigators can connect the man to the earlier crash. Those questions are distinct from what authorities have confirmed so far: one officer died, three were wounded, the man was killed by police, and the transit agency identified the bus as a Route 76 vehicle.