It was a good thing on Thursday that the streets of downtown SF still aren't very busy, because a big pane of glass fell from a skyscraper and shattered on the sidewalk β€” and no one was injured.

While a 45th-floor window was in the midst of repair on Thursday afternoon, the glass fell all 45 stories down. The San Francisco Department of Emergency Management issued an alert on Twitter at 2:08 p.m. Thursday, telling residents to avoid the area of First and Folsom streets due to "an obstruction."

There was no mention of what was actually going on until 2:35, when the SF Fire Department posted the photo below β€” showing suspended scaffolding like window washers use, hanging right around the 45th floor of the 55-story Avery tower at 450 Folsom. The department confirmed there had been no injuries.

The window glass seems to have come loose while it was undergoing repair.

Because Twitter is Twitter, someone took the time to whine to the Dept. of Emergency Management's that perhaps their alerts about avoiding areas should be targeted only to drivers, because "I doubt that pedestrians should be avoiding the area."

And someone else soon replied, "Considering a window fell from a 45 story building, I think it was prudent for pedestrians to avoid the area."

Back in February 2020, a large window fell from the 41st floor of Millennium Tower, shattering on the ground and thankfully injuring no one β€” but that incident was blamed on a big wind gust and the fact that the window was open at the time.

The scary situation at 450 Folsom is also reminiscent of the infamous early days of Boston's John Hancock Tower, designed by I.M. Pei, which began dropping 500-pound pieces of glass in high winds during its construction in the early 1970s. So many pieces of glass fell and were temporarily replaced with plywood that the tower was nicknamed the "Plywood Palace." The opening of the tower was delayed five years as a result of the problem, from 1971 to 1976 β€” and all 10,334 panes of glass had to be replaced due to a design flaw.