PHILADELPHIA (AP) — A 17-year-old who was in a car stopped for an expired car registration sticker traded gunfire with police during a Tuesday morning highway chase that ended with a fiery crash involving a school bus and a trooper with a gunshot wound, police said.

Trooper Patrick R. Casey suffered a "flesh wound" to his shoulder, state police Capt. James Raykovitz said.

The teen and a second person who was in the car when it was stopped were in custody as police searched for two more people following the midmorning crash on a downtown highway, authorities said.

When police first stopped the car, they asked the four people inside to exit the vehicle, but one of the suspects jumped back in and took off, investigators said.

Trooper Patrick R. Casey, providing backup, pursued the car, at one point getting in front of it to try to force a stop, authorities said. The suspect instead rammed Casey's cruiser, then pulled alongside him and opened fire, Raykovitz said.

The suspect then crashed into the school bus, causing both vehicles to burst into flames. The bus was empty except for the driver, who escaped unharmed. The suspect again started shooting, while Casey returned fire, authorities said.

Casey, 31, was struck once in the shoulder.

"He performed heroically, as best as he could, given the situation," Raykovitz said.

Casey was in good condition later in the day, discussing holiday plans during a phone call with Gov. Tom Wolf.

"The governor was glad to hear that Trooper Casey believes he will be able to be home with his family for Thanksgiving," Wolf's office said in a statement.

The identities of the 17-year-old and the second suspect in custody were not immediately released. Police said the second suspect, a man in his early 20s, had given police a false name when the teen took off in the car.

Steve Glowacki was working nearby when he saw the shooting.

"I saw a gunfight down here," he said while pointing to Interstate 676 from an overpass. "I came out, there were cops down there, shooting at someone, and then someone was shooting at them."

He said he saw state police troopers with guns drawn.

"I heard what I thought was gunfire, and it turns out that it was," he said. "When I came out, there was a gunfight going on and that car had already hit the bus."

Video posted on social media showed law enforcement officers running down the closed section of I-676 and apprehending one man.

A newspaper reporter on her way to an assignment was on the highway when she saw the police chase, heard gunfire and then saw flames erupt from the crash scene.

Kathy Lauer-Williams of The Morning Call, in an account posted on the Allentown newspaper's website, said she saw a police cruiser try to box in the getaway car, but the car then swerved into the cruiser, sending debris flying.

Authorities said some good Samaritans were also involved in the capture of the suspects.

The busy stretch of road was closed in both directions between Interstate 76 and Interstate 95, but it reopened later in the day.

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Associated Press writers Kathy Matheson in Philadelphia and Mark Scolforo in Harrisburg contributed to this report.