MIDDLETON, Wis. — Authorities say they still don't know why a Wisconsin software company employee went to his office with a pistol and extra ammunition and opened fire on his colleagues, seriously injuring several before he was fatally shot by police.

The attack happened Wednesday morning at WTS Paradigm in Middleton. Investigators haven't released the suspect's name but say he lived in nearby Madison.

Middleton Police Chief Chuck Foulke says three victims suffered serious injuries, while a fourth suffered a graze wound.

Foulke says officers were on the scene and shot the man within eight minutes of getting an emergency call. Foulke says the man was using a semi-automatic pistol and had extra magazines, and that he believes officers prevented more bloodshed.

He says the man fired at officers before he was shot.