ALBUQUERQUE (Reuters) - A New Mexico man accused of killing a four-year-old girl by shooting her in the head in a road rage incident last week was also charged on Friday (Oct 30) with federal firearms and drug trafficking offenses, court records showed.

Tony Torrez, 32, has admitted fatally shooting the child, Lilly Garcia, when he opened fire on her parents' truck after cutting them off on Interstate-40 in Albuquerque and exchanging words with her father, the police say.

As well as charges including first-degree murder and child abuse resulting in death, Torrez is also charged with possession of marijuana with intent to distribute, and possessing a firearm in furtherance of a drug trafficking offence.

According to an affidavit filed by a US Drug Enforcement Administration special agent, when investigators received a tip-off about the killer's identity they went to Torrez's home and found marijuana, scales, and boxes of cash.

Two assault rifles, a revolver handgun, ammunition magazines, cocaine, and more cash were then discovered in two vehicles associated with Torrez, court papers showed.

The affidavit said US$64,000 was recovered from the house and cars, "consistent with proceeds from drug trafficking".

The murder of Lilly in front of her parents and her seven-year-old brother in a mid-afternoon confrontation beside a busy highway shocked New Mexico's biggest city.

Torrez is being held in the Bernalillo County Metro Detention Centre on a US$650,000 cash-only bond. No attorney was listed for him in online jail records on Friday.