SAN DIEGO -- A 45-year-old wheelchair-bound man was arrested on suspicion of wounding his wife by firing two gunshots into her chest as she drove on Interstate 5 in Clairemont Mesa, San Diego police said Thursday.

Riding with his wife in a van, the man pulled a small-caliber handgun and fired on her as she drove on the southbound I-5 near Balboa Avenue just before 5 p.m. Wednesday, Sgt. Rich Nemetz said.

The woman pulled off the freeway and drove to the 4300 block of Berwick Drive, where a passer-by called police, Nemetz said.

The woman was taken to a San Diego hospital, where she was treated for two gunshot wounds to her chest, Nemetz said. She is expected to survive.

The man, who is paralyzed from the waist down, was arrested, Nemetz said.

The couple, whose names were not released, had apparently gotten into an argument just before the shooting, Nemetz said. It was unclear what they were arguing about.

The police department's Domestic Violence Unit investigated the shooting, Nemetz said.