DALLAS (CBSDFW.COM) – A man charged with capital murder is accused of sexually assaulting his grandmother and then beating her to death with a fire extinguisher at a home in Dallas, according to an arrest affidavit.

Police arrested Michael Robinson, 32, after officers responded to a home on Terry Street Saturday morning and found the victim, 71-year-old Irish Harrison, dead in her bedroom.

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According to the affidavit, Robinson went to the home to visit his grandmother when he allegedly began sexually assaulting her and then punched and kicked her in the head and body.

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The 32-year-old then struck her “several times” in the head with a fire extinguisher, which led to her death, according to the affidavit.

Michael Robinson (Source: Dallas County Jail)

Police said witnesses went to the home Saturday morning and found Harrison dead and Robinson in the living room. Police soon arrived and arrested the suspect at the home.

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Police said Robinson admitted to sexually assaulting and killing his grandmother. He was taken to jail and charged with capital murder.