SEATTLE >> Authorities in the Seattle area are searching for a 17-year-old boy who they say shot and killed a passenger on a city bus last month in what newly filed charging documents describe as “the senseless execution of a total stranger” — a recent example of shocking but rare attacks on public transit around the country.

Miguel Rivera Dominguez was charged Wednesday with first-degree murder and second-degree unlawful possession of a firearm. He is wanted in the death of Marcel Da’jon Wagner, 21, who appeared to be sleeping when he was shot on board a bus in White Center, an unincorporated neighborhood just south of Seattle, on Oct. 3, the King County prosecutor’s office said.

Court documents did not list an attorney for Rivera Dominguez who might speak on his behalf, and a voicemail left Wednesday for a couple identified in charging documents as his guardians was not immediately returned. The teen had no prior criminal record, Casey McNerthney, a spokesman for the prosecutor’s office, said in an email.

King County Metro boosted security on the H Line, which runs between downtown Seattle and the south suburb of Burien, after the shooting, spokesman Al Sanders said in an email today.

Since early last year, the agency has doubled its number of unarmed security guards to 140, for a system with about 7,000 bus stops and about 240,000 daily riders. It also has about 60 Metro Transit Police officers, about 20 fewer than its budget would allow, owing to staffing shortages that have proved a challenge for departments around the country.

Last month, a man who sprayed a New York subway car with bullets in April 2022, injuring 10 people, was sentenced to life in prison. Just two months earlier, a woman was shoved to her death at the Times Square subway station. And in September, a man was stabbed to death on a Los Angeles subway “without warning or provocation,” authorities said.

An Indiana woman faces a federal hate crime charge in the stabbing of an 18-year-old college student of Chinese descent on a public bus early this year, and last year an 82-year-old man was fatally beaten at a bus stop in Portland, Oregon.

According to charging documents, Rivera Dominguez was on the bus for about 15 minutes, wearing a full-face ski mask, when he pulled a cord requesting a stop. He then shot Wagner “without any provocation, and in fact without having ever interacted with the victim at all,” deputy prosecutor Lauren M. Burke wrote in requesting that bail be set at $3 million should he be arrested.

“The defendant’s senseless execution of a total stranger strongly suggests that if released on his own recognizance or on a low bail, he will commit future violent offenses,” Burke wrote.

There were about a dozen other passengers on the bus who appeared stunned by the gunfire, including a 17-year-old boy who was with Rivera Dominguez, King County sheriff’s detective John Free wrote in a probable cause statement, citing bus surveillance video. The attacker then fired two shots through the rear doors of the bus and left with the friend, authorities said.

The statement said investigators identified Rivera Dominguez by following the pair via residential and business surveillance cameras, eventually tracking them to a neighborhood in Burien where a detective knocked on a door and was advised by the resident that there was a teenage boy living nearby.

Investigators used the address to identify the boy as Rivera Dominguez through a prior report that he had run away from the home. Free began investigating him and also learned the identity of the friend through a security official with the Highline School District.

The detective said investigators eventually questioned the friend, who confirmed that Rivera Dominguez was the shooter, and they found surveillance footage from a Boys and Girls Club showing that he changed clothes and removed his mask in a locker room just after the shooting.

The boy “stated he had no forewarning that Dominguez was going to shoot anyone and that neither he nor Dominguez even knew the victim,” Free wrote.