This sequence is correct. (At what point they knew she had been shot, I don't know if we know that. It may have been obvious from the outset.)The search warrant stating she suffered multiple puncture wounds found on her head and chest consistent with tools the suspect was carrying thought the building was issued the day after MB was killed. They didn't know a gun was involved until the autopsy was performed.
But it may not be saying what you have in mind with those details, because as gliving noted, the autopsy was done as a priority and autopsy results were said to be back and available to LE the morning of day 2, BEFORE the day 2 SW (which was done around 6 pm on day 2). The news report on the afternoon of day 2 says "In a written statement, Chief Kevin Johnson said the Dallas County Medical Examiner's office completed an autopsy on Bevers Tuesday morning. "In the interest of the ongoing investigation, we are not releasing any details ... at this time," he said."
This leads to an interesting possibility about the odd SW wording. What if the person writing up the SW had just read the autopsy report before doing the SW? Obviously the autopsy would be tasked with describing the body and its wounds precisely. So in the SW they simply parrot the autopsy wording that there were "puncture wounds to the head and chest" (which explains the origin of that odd terminology), adding that the video fits in some way, and that's how we get to where we are.