MADISON, Wis. (AP) — A former co-worker says a gunman who opened fire at a Wisconsin software company was quiet and never smiled.

WTS Paradigm employee Anthony Tong shot four co-workers at the company’s Middleton headquarters Wednesday before police killed him. All the workers survived their injuries.

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Tong’s motive remains a mystery.

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Isaac Hall tells the Wisconsin State Journal he left the software company for a new job a week before the shooting. He says Tong never talked and never smiled. He says Tong “creeped” him out.

Former Madison Alderman Chris Schmidt said he and Tong were both in the physics program at Lawrence University in the mid-1990s. He says Tong studied often in the library and was interested in computers, but was as a sociable as anyone else.

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