An appliance delivery man bashed an elderly woman’s head with a mallet before dousing her with a liquid chemical that spontaneously combusted and ultimately killed her, police in South Florida said Tuesday.

Officers in Boca Raton responded to an emergency call from the woman's home at around 9:15 a.m. Monday, a police affidavit said.

Paramedics found the unconscious woman lying on the floor with blunt-force injuries to her head and severe burns over her body, police said.

Police encountered a man at the home, 41-year-old David Gonzalez, who told them that he and his coworker, 21-year-old Jorge Luis Dupre Lachazo, had delivered a washer and dryer to the woman’s home, the Miami Herald reported. The men reportedly work for the delivery company JB Home Delivery, a subcontractor of Best Buy.

Gonzalez told police he had gone outside to make a phone call after he and Lachazo had installed the appliances. Lachazo stayed inside to talk to the woman about the new appliances, he said.

After he heard screams inside the home, Gonzalez said he went back inside and saw blood and the woman lying on the floor. He said he went outside to call 911 while Lachazo got in their truck and drove away.

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A responding officer saw the truck and pulled over Lachazo, who was sweating and shaking, the Sun-Sentinel reported. Paramedics reportedly took him to a nearby hospital for treatment.

The woman was rushed to a hospital where she died Tuesday from her injuries, police said. Her identity was not released.

Investigators said Lachazo admitted during an interview that he hit the woman with a mallet then doused her with the chemical. Police said he also admitted to using cocaine and marijuana earlier in the day.

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He’s been charged with first-degree murder, armed burglary with battery and arson, police said.

Best Buy’s CEO said in a statement the company will no longer do business with JB Home Delivery, which could not be reached for comment.