PHILADELPHIA — Two 18-year-olds were arrested in the shooting of eight Philadelphia high school students at a bus stop last week, and authorities recovered a fully loaded, fully automatic weapon that matches evidence found at the scene, they announced Monday.

Two more suspects were still being sought, authorities said. The Wednesday afternoon shooting was the fourth in four days involving the city’s transit system.

The discovery of the stolen car involved, just hours later, helped lead police to suspect Jamaal Tucker, who turned himself in Friday, police said. On Saturday, they said, federal marshals searched a location linked to Ahnile Buggs and recovered the .40-caliber Glock that matched casings found at the scene.

Both teens are currently facing the same charges, including attempted murder, aggravated assault, weapons offenses and other charges, and are being held on more than $2 million bail. Preliminary hearings are scheduled March 20 for both. A message left Monday with Buggs’ attorney was not immediately returned. Tucker is being represented by public defenders, who did not immediately respond to a message seeking comment.

Mayor Cherelle Parker led a group of public officials at a Monday afternoon news conference, including the heads of the local FBI and Bureau of Alcohol, Tobacco, Firearms and Explosives offices, to try to assure anxious city residents they are working to address the spate of transit crime.

“We will focus on prevention, intervention and enforcement,” said Parker, who took office in January and promised to present her public safety strategies in the coming weeks “in an effort to bring lawfulness and some order back to our city.”

She urged an end to the finger-pointing that has caused friction between the police department, reform-minded District Attorney Larry Krasner and other agencies in recent years.

The shooting Wednesday came as students at nearby Northeast High School were waiting to board the bus home.

At about 3 p.m., three masked suspects rounded the corner and opened fire, surveillance video shared by police shows. The victims were ages 15 to 17. All of them are now in stable condition, police said Monday, including a 16-year-old who was critically injured after being hit nine times.

The city’s police commissioner, Kevin Bethel, credited quick action by two police officers in applying tourniquets to three of the victims with possibly saving lives.

Northeast High School is the largest public high school in the city, with more than 3,000 students.

Police were investigating whether the shooting may have been related to the fatal shooting of a 17-year-old charter school student, when gunmen fired 40 shots at close range as people boarded a city bus in the city’s Ogontz section. Four others were injured, including a 70-year-old woman.

Also last week, police believe an argument aboard a bus led a 37-year-old man to be fatally shot by a passenger exiting a bus in South Philadelphia. And a 27-year-old man was killed by another passenger moments after they both got off a bus in the city’s Oxford Circle area.