The falling piece of space junk is the core stage of a Chinese Long March 5B rocket.
The rocket launched on Sunday, July 24th, 2022, taking the Wentian module for China's Tiangong space station to orbit, the second module for the under-construction space station. Experts estimate that the rocket stage will stay in orbit for about a week before re-entering Earth's atmosphere on July 31st, around 3:30 a.m. EDT (07:30 UTC), plus or minus 22 hours, and then crashing to the ground to an as-of-yet unknown location.
The Aerospace Corporation noted that about "20-40% of the mass of a large object will reach the ground," meaning 5-9 tonnes (5.5-9.9 tons) of rocket will reach Earth, with the rest burning up in the atmosphere. The uncontrolled return of the Long March 5B rocket is the second of its kind, after an identical rocket did the same after delivering the first module of the Tiangong space station, Tianhe, to orbit on April 29th, 2021.