BOSTON (AP) — No criminal charges will be filed against a Massachusetts State Police trooper who fatally shot a man wielding a knife in 2015.

Suffolk County District Attorney Daniel Conley says Trooper Andrew Patterson was acting in self-defense when he shot Santos Laboy on a footbridge near the campus of Boston University.

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The prosecutor announced his findings Wednesday after reviewing the case.

Santos Laboy was shot and killed by a State Police trooper in Boston (Credit: Dr. Elizabeth Chabner Thompson)

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His investigation found that Laboy was approaching Patterson with a three-inch blade at a distance of about 20 feet away when Patterson shot him four times. Conley said the trooper was moving backward when he shot and had ordered Laboy to drop the knife.

Patterson was responding to a radio call for help as Boston University police officers chased Laboy, who was being sought in connection to an earlier investigation.

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