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May 4, 2015, 3:13 AM UTC / Updated May 4, 2015, 6:43 PM UTC / Source : NBC News

An Air Force veteran shot and killed three people, then himself, on a Wisconsin bridge on Sunday night, police said. Another person was critically injured.

Investigators believe the shooter, identified as Sergio Daniel Valencia del Toro, 27, randomly started firing two handguns on the Fox Cities Trestle Trail Bridge after an argument with his girlfriend, police in Menasha said.

The girlfriend had already left del Toro when he began shooting. Killed were Jonathan Stoffel, 33; his 11-year-old daughter, Olivia; and Adam Bentdahl, 31, Police Chief Tim Styka said. Styka said del Toro, who was a student, shot all of the victims at close range and was “unprovoked.”

Jonathan Stoffel’s wife, Erin, 32, got two of their children off the bridge safely. She was shot three times and hospitalized.

SOCIAL

Scene near Tressle Bridge in Menasha the site of reported shootings pic.twitter.com/z2sIlbc0YR — Ricardo Arguello (@PCRicardo) May 4, 2015

Praying for all those involved in the Menasha shooting — Esther Willoughby (@Estherhwillow) May 4, 2015

— M. Alex Johnson and Elisha Fieldstadt