Police said they were quickly able to arrest an 18-year-old for shooting a person on a Pittsburgh Regional Transit bus last weekend in part because the teen showed his face on camera and used a phone app to pay for his fare.

Michael Andrews of Pittsburgh was charged with shooting a person he “has been having beef with,” after the two argued on a bus traveling on the transit agency’s East Busway, near Pittsburgh’s Homewood neighborhood, according to a criminal complaint.

Port Authority police Monday charged Andrews with aggravated assault, reckless endangerment and two gun counts. He was arraigned Tuesday, court records show.

Andrews remains in the Allegheny County Jail without bail. His attorney was not listed Tuesday in online court records.

Police said Andrews and an unnamed woman boarded the bus at 4:42 p.m. Saturday using the transit agency’s Ready2Ride app. They were two of five different riders whose “taps” through the Ready2Ride app were reported on the bus between 4:41 p.m. and 4:44 p.m.

Video from inside the bus showed Andrews argue with the victim, who was walking toward the rear, the complaint said. Footage showed Andrews and the victim “face to face,” according to the complaint.

Police said Andrews pulled “a black object” from his waistband during the argument and shot the victim once in the chest. Gunfire shattered part of a skylight above passengers, causing broken glass to fall into the bus.

The victim, who police have not named, ran off the bus toward the busway’s Homewood station, the complaint said. Andrews and the unnamed woman fled.

First responders took the victim to an area hospital in critical but stable condition, the complaint said.

Andrews was wearing a sheisty — or ski-mask-style face covering — during the confrontation but it was “pulled down, exposing his entire face,” the complaint said.

Police for the Southeastern Pennsylvania Transportation Authority, or SEPTA, banned full-face ski masks, or sheisty masks, in 2023 on all buses, trains and stations after a spate of robberies and shootings.

A juvenile probation officer watched Saturday’s footage and identified the shooter as Andrews, the complaint said.

That officer, who was Andrews’ probation officer, also showed authorities a photo of Andrews from Instagram, the complaint said. In it, Andrews wore black and purple Air Jordan 12 sneakers, “a unique and distinct” article of clothing investigators said the shooter wore on the bus.

Police interviewed five different witnesses to the bus shooting.

One of them said Andrews, known in music videos by the street name “Rackz,” commonly carried what he called a “wheel gun,” the complaint said. The pistol had a “unique” cylinder that stopped shell casings from being ejected from the gun after a shot was fired.

Police did not find any shell casings on or near the bus.

Port Authority police took to social media this week to announce Andrews’ arrest — “less than 48 hours after the shooting,” the department said on social media.

“Thanks to a strong department-wide, collaborative effort, detectives and officers quickly brought this investigation” to a close, the police department wrote.