More than six witnesses told Richardson police they saw the startling incident unfold on the 85-foot-tall Bush Turnpike overpass late Thursday, The Dallas Morning News reported.
The couple was first seen arguing inside a parked 2000 Mercedes on the shoulder and then they got out. One witness said at first he thought they were just "goofing" around.
"I saw him trying to throw her over. And she was doing her best to stop him. She was fighting like hell," said witness Henry Ford of Plano.
Ford said he pulled over to the shoulder ahead of the Mercedes and was getting out of his car when the man pushed the woman over the railing and then jumped himself.
The woman's body fell on the hood of car passing below on the North Central Expressway and was carried a short distance before the car was struck by another vehicle, police said. The man was transported to a nearby hospital where he died.
The couple lived in a Dallas apartment, said police, who have no idea what precipitated the dispute.