WOODBRIDGE (CBS13) – A man was badly injured after opening the door to his MMA-trained teenage neighbor who then severely beat the man, according to authorities.

On Monday, just after 7:30 p.m., a man says he heard a knock on the door. After seeing that it was his neighbor, he opened the door and that’s when he was suddenly attacked — with no explanation, according to the San Joaquin County Sheriff’s Office.

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Surveillance video caught 19-year-old Juan Ramirez punching and kicking the man, then hitting him across the face with baseball-sized rocks. Ramirez then allegedly dragged the man across his property.

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The victim was subsequently taken to the hospital where he was treated for abrasions on the top and back of his head, cuts and bruises throughout his body, broken ribs, a collapsed lung, and a ruptured eardrum. He was also examined for a possible broken jaw and a broken wrist.

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Ramirez, who claims he has MMA training, was booked into the San Joaquin County Jail on charges of assault with a deadly weapon, felony battery, and mayhem.