Police are trying to figure out why a Gwinnett County man strangled a woman and her 2-year-old son.

A towel was used in the woman's death and an unknown "offensive object" was used in the toddler's death, according to arrest warrants.

Authorities responded to the 2700 block of Tybee Drive near Buford about 11 p.m. Sunday after they got a call from the homeowner.

Officers are investigating a 2-year-old boy's death as a homicide Monday. (Credit: Gwinnett police)
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“The caller reported that his son had choked a mother and child that live at the house and walked a short distance up the street to a gas station,” Gwinnett police Cpl. Deon Washington said.

The incident happened while the homeowner was outside working on a car in the driveway, according to police. The woman, identified in the arrest warrant as Natalie Nation, was renting a room at the home, the homeowner told authorities.

Both victims were taken to the hospital. The toddler, who Channel 2 Action News identified as Cole Nation, died first. Hours later, police said the mom died at Gwinnett Medical Center.

Police confronted the suspect at the gas station and arrested him without incident. Brandon Williams, 32, of Buford, is in the Gwinnett County Detention Center without bond on multiple charges, including one count of felony murder and two counts of aggravated assault.

Brandon Williams (Credit: Gwinnett police)
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"Fortunately, this was an isolated incident and police are not searching for any additional suspects,” Washington said.

There are no family ties between Williams and the victims, according to police.

In other news:

A tractor-trailer crashed with an SUV, spilling chemicals onto the road Monday morning.