Miscommunication and an improperly marked gas main were to blame for an explosion last summer that killed a Wisconsin firefighter, injured 11 other people and leveled a city block, authorities said Thursday in announcing that no one would face charges.

The July 10 blast that rocked downtown Sun Prairie happened about 40 minutes after a subcontractor who was installing fiber communication lines struck the gas main, Patrick Anhalt, the police chief of the southern Wisconsin city, said at a news conference.

Police, firefighters and other emergency personnel raced to clear the area, including firefighter Cory Barr, who owned a downtown restaurant along with his wife, Abby. Barr was off duty, but he rushed to the scene to help evacuate people and was leaving his restaurant with another firefighter when the explosion occurred.

Barr was killed in the blast and 11 other people, including five other firefighters and a police officer, were injured. Among the six businesses that were destroyed was the Barrs' tavern, the Barr House. One home was also destroyed.

Authorities released dashcam video Thursday that was taken from a squad car that was parked about half a block away from the site. It shows what appears to be five utility workers in hard hats and reflective vests crossing the street as the building erupts in a massive explosion. They run away as debris rains down and a plume of smoke rises.

Companies working to install the underground fiber-optic line exchanged and relied upon "incomplete and inaccurate information," Anhalt said. Police, the county district attorney, state fire marshal and Wisconsin attorney general's office all agreed that criminal charges weren't warranted, he said.

The chief blamed the accident on "miscommunication" but didn't explain what exactly happened or whether such a mistake can be prevented from happening again. He said investigators conducted 67 interviews and examined 45 pieces of evidence and 400 pages of documents during their five-month probe.

Neither Anhalt nor any of the other officials who were at the news conference fielded questions, but they did make public a redacted copy of the investigation report.

Abby Barr did not immediately reply to a message Thursday seeking comment about the decision not to criminally charge anyone. According to WKOW , she filed a wrongful-death lawsuit Thursday naming VC Tech, Bear Communications, USIC Locating Services and WE Energies as defendants. Two firefighters who were injured, Ryan Welch and Greg Pavlik, also filed suits Thursday with the same companies listed as defendants.

WE Energies spokesman Brendan Conway said the Milwaukee-based company had not received or reviewed the lawsuits, but does not comment on pending litigation.

Sun Prairie, a city of about 30,000, is just to the east of Madison, Wisconsin's capital city.

In a search warrant request in which investigators were looking for evidence to support a second-degree reckless homicide charge, authorities said a worker for Wisconsin-based USIC, an underground utility locating firm, failed to properly mark a natural gas line prior to the explosion.

Anhalt said Verizon Wireless contracted with Bear Communications for the fiber optic installation project. Bear Communications first subcontracted with Jet Underground, but then changed subcontractors to Michigan-based VC Tech, he said.

VC Tech proceeded with the project and, while engaged in "underground directional boring," cut through a WE Energies gas line that was not completely marked, the chief said.

About 40 minutes later, the escaping gas ignited. The cause of the ignition was not determined, Anhalt said.

"This error appears to be the result of miscommunication between USIC, Bear Communications, Jet Underground, and VC Tech," Anhalt said. "Prior to the explosion, conversations occurred between representatives of each of these companies, both on and off site, during which incomplete and inaccurate information was exchanged and relied upon."

Anhalt said the explosion could result in a law change to improve communication between companies involved in underground utility work.

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