It sounds like they saw three militants in an abandoned building, got in a firefight therewith, hit the building with a tank, and found his body in the rubble.
They didn't know it was hit at the time, but it really looked like him, so photos of him with a giant hole in his head hit Twitter pretty fast and it was pretty unmistakable, but DNA testing has confirmed it now.
No hostages or civilians were in the building. It's not clear what he was doing above ground. This lends credence to the speculation that all the hostages Hamas had are dead or sold at this point.
Hopefully this leads to the end of the war. Between Hamas seemingly running out of hostages and those responsible for October 7 mostly dead, it seems like most of the barriers to peace are gone.