Police believe that they may have apprehended a serial killer linked to nine murders who was arrested after allegedly shooting dead his mother and stepfather in Arizona.

Authorities believe that Cleophus Cooksey Jr. may be behind nine slayings and a sexual assault in the Phoenix area that culminated in the slaying of his mother, Rene Cooksey, 56, and her husband, Edward Nunn, 54.

Cooksey was arrested inside his mother's home on 17 December after the two victims had been shot dead.

Now the 35-year-old is charged with nine counts of first degree murder, eight counts of possession of a gun as a felon, theft of a gun, armed robbery and sexual assault.

He is believed to be behind nine killings in the last three weeks of the year that including a friend, the brother of his ex-girlfriend but also complete strangers, or people he met online.

Cooksey's first alleged killing was on 27 November when he shot and killed Andrew Remillard, 27, and 21-year-old Parker Smith in what may have been a random attack, AZ Central reported.

He then allegedly killed Salim Richards, 35, on 2 December, the brother of his ex-girlfriend 25-year-old Jesus Bonifacio Real, Latorrie Beckford, 29, on 13 December.

Then on 15 December 21-year-old Kristopher Cameron was found shot and bloodied, kneeling in a grassy field and died the next day.

On 16 December Maria Villanueva, a 43-year-old woman allegedly got in the car with Crooksey before he sexually assaulted her then killed her and dumped her body.

Cooksey's alleged murder spree came to an end the next day when police discovered the dead bodies of Rene and Nunn in the living room of their home after they received a 999 call.

While in custody police were able to use the ballistics from his guns and additional evidence to connect him to the other murders, it was reported.

Phoenix police Sgt. Jonathan Howard said: "To solve nine homicides in a period of three weeks is outstanding."