A man wounded himself in an apparent attempted suicide after killing his wife and their two daughters, aged four and one, in Orange Farm on Friday morning, police said.

Spokesperson Johannes Motsiri said the man's great-grandmother was visiting his family when a fight broke out at 8am.

"It is alleged that the wife was asking about money for the building materials as they are extending the house and the contractor was there," Motsiri said.

Seeing that the man, employed as an ambulance attendee, was getting angry, the older woman went for help.

He shot his 25-year-old wife before locking himself inside the house and shooting their daughters.

He then turned the gun on himself, but survived and was in a critical condition in the ChrisHani-Baragwanath Hospital, said Motsiri.