A massive U.S. fishing boat smashed into a Canadian navy ship early Tuesday in Esquimalt, sending six people to hospital and leaving many wondering what went wrong.

A Seattle-based fishing trawler was being towed into dry dock by two tug boats when one of the boats nearly rolled over, one witness said.

“They cut the line loose and then it just shot across the harbour and ran into one of the frigates,” he said. “Just the collision itself would be like an earthquake…there would be people flying all over the place.”

As the boat smashed into the docked navy ship HMCS Winnipeg, two giant waves of water cascaded down on both ships, leaving six people with minor injuries.

Rob Patterson was on board the frigate when the devastating crash occurred. He was standing on a ladder doing cabling work when he suddenly went flying.

“The boat moved about 20 odd feet, tossed us around and that was it. We didn’t know what happened,” he said. “The boom was incredible. I’ve heard car crash booms, but that was like somebody beating on a big drum…an incredible noise I don’t want to hear again.”

The two tug boats are owned by North Vancouver-based Seaspan Shipyards. The company is also doing a massive refit on HMCS Winnipeg.

Seaspan president Brian Carter said 64 people in total were working aboard the Winnipeg at the time of the incident.

Six workers sustained minor injuries and are all recovering at home, he said.

Canadian Forces Base Esquimalt said it’s still assessing the damage to the Winnipeg, while it’s up to the Transportation Safety Board to determine the cause of the crash.

With a report from CTV British Columbia’s Jina You