A man who allegedly shot his son Friday has been arrested and charged with one count of aggravated assault, police said.

Joseph Valenta, 79, originally called police to report an intruder at about 5 p.m. Friday, said Phoenix police spokesman Steve Martos. When police arrived at his home, in the area of 39th Avenue and El Caminito Drive, they discovered that Valenta’s 53-year-old son had been shot.

The victim was taken to an area hospital, where he remains in critical condition, Martos said.

During questioning, the father admitted that he had been involved in the crime, which investigators believe stemmed from ongoing arguments between the two, police said.

The son had been living in a parked car in his father’s driveway, police said.