“I told them to leave,” Walter said when he was able to speak with us later.

“They didn’t have to be there at all.”

Gavin explained the sequence slowly.

One wheel of the handcart caught on broken concrete.

A stack of bicycle frames slid against a loose support panel.

The movement dislodged the old brace holding it in place.

“It was loud,” he said.

“Like a car door slamming against a building.”