https://www.brennancenter.org/our-work/research-reports/poli... has a list of police body cam retention policies. 90 days is pretty common, though it ranges from 30 days to 5 years.

Documents are kept longer. But a court needs to think about the shortest possible retention time that any agency might have for any kind of evidence.

From your link's subheading:

> This chart includes categories for how long video is kept if it does not contain evidence of a crime [emphasis added]

So yes, some things are short (I did write "usually" for a reason), but even your link doesn't claim that video of a killing would be deleted in 90 days. It's evidence, 90 days would be ridiculously short for retaining evidence.

Even for people who don't think the ICE agents committed a crime, the ICE agents and DHS have claimed that this was the outcome from actions by a "domestic terrorist" which certainly makes it evidence of a crime from their own perspective.