CHICAGO (AP) — Investigators studied the crash scene Friday after a Southwest Airlines jet trying to land amid heavy snow plowed off a Midway International Airport runway and into a street, killing a 6-year-old boy in a car.

Ten other people, most of them on the ground, were injured in the Thursday evening accident, authorities said. The accident, the first fatal one in Southwest’s history, closed the airport overnight but it reopened at 6 a.m., Aviation Department spokeswoman Wendy Abrams said.

Flight data and cockpit voice recorders were removed from the plane and were being sent to Washington for analysis, a National Transportation Safety Board investigator said Friday.

Flight 1248 from Baltimore with more than 100 people aboard touched down around 7:15 p.m. Thursday. Though the airport had about 7 inches of snow, aviation officials said conditions at the time were acceptable.

The plane went off the end of the runway and slammed through a fence before it struck two vehicles, pinning one beneath it. The boy who died, one of five people in the pinned car, was identified as Joshua Woods of Leroy, Ind., said Sandra Flowers of the Cook County Medical Examiner’s office.

Passenger Mike Abate, 35, of suburban Milwaukee, said he could see from the plane that a man was carrying an injured child and that other people were taken away in an ambulance.

``We were safe on the plane,’’ Abate said. ``The toughest part was to realize that someone was under the belly of the plane.’’

The Boeing 737, nose resting on the ground, and the vehicles remained in the street Friday morning. NTSB investigators were on scene.

Southwest CEO Gary Kelly said Friday morning it was the first fatal accident involving a Southwest flight in the discount carrier’s 35-year history.

MIAMI — Shortly after boarding an Orlando-bound plane, passengers say, they saw a man bolt from his seat and run down the aisle, with his screaming wife and man in a Hawaiian shirt behind.

“My husband! My husband!” one passenger said she heard the wife cry.

Before he ran off the plane he “uttered threatening words that included a sentence to the effect that he had a bomb,” said James E. Bauer, agent in charge of the Federal Air Marshal Service field office in Miami.

The chase ended moments later Wednesday in a Miami International Airport jetway, when authorities say Rigoberto Alpizar appeared to reach for his bag. He was shot to death by the man in the Hawaiian shirt and a second pursuer, both undercover air marshals.

No bomb was found, and federal officials later concluded there was no link to terrorism. Witnesses said his wife, Anne, frantically tried to explain he was bipolar, a mental illness also known as manic-depression, and was off his medication.

“She said it was her fault, that he was bipolar,” said Mike Beshears, a Flight 924 passenger. “He was sick and she had convinced him to get on the plane.”

It was the first time since the Sept. 11 attacks that an air marshal discharged a firearm at a passenger or suspect, said Homeland Security Department spokesman Brian Doyle.

Dave Adams, a spokesman for the air marshals, confirmed Thursday there were two marshals on the flight and said both fired at Alpizar.

He said the marshals followed proper procedures.

“We only react when there is a threat to the aircraft, passengers or crew,” Adams said.

The Bush administration hired thousands of additional air marshals after Sept. 11, when the nation had only 33. The exact number is classified. Marshals fly undercover, and which planes they’re on is a closely guarded secret.