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A Maitland, Florida police officer fatally shot 18-year-old Alexander May as he continued stabbing his mother during a 911 call, and prosecutors later ruled the shooting justified, authorities said.

Diana May called 911 around 6:45 a.m. on Aug. 3, 2009, after her son attacked her with a knife inside their home in Maitland's Dommerich Estates neighborhood, according to a police report and 911 recording released by authorities. A dispatcher told her to lock herself inside a bedroom, but her son forced his way through another door and resumed the attack.

Two Maitland officers followed a trail of blood to the bathroom, where they found Alexander May kneeling over his mother and stabbing her with a 16-inch barbecue fork, Maitland Police Chief Doug Ball said. Officer Steve Mendez ordered him to stop, and investigators said Alexander May paused with his arm raised, "a smirk on his face," before turning back and striking his mother twice more. Mendez shot him twice in the chest, killing him, police said.

Diana May, 60, survived with multiple stab wounds. She disputed investigators' account, telling authorities and reporters that Mendez fired before ordering her son to drop the fork, whose tines had already been bent 90 degrees from the force of the attack. "That officer has to live with his conscience," she said. "I am mourning the death of my son."

Mendez, 35, an eight-year veteran of the department, was placed on administrative leave, which is standard after police shootings. The Florida Department of Law Enforcement investigated, and the state attorney's office released hundreds of pages of evidence in November concluding Mendez was justified. He had already returned to duty weeks earlier.

Investigators said they could not determine why Alexander May attacked his mother. An autopsy found no evidence of illegal substances. A friend told investigators May had not slept in three days and seemed stressed about leaving home for college that fall. May had graduated from Winter Park High School earlier in 2009.