The referenced article is not new. It was published in 2022.

I'm sceptical that it is the first-ever recording of a dying human brain. I recall significant interest in and controversy regarding changes in EEG recordings around the time of death back in the 1980s and EEG was in use and the issue was controversial for decades before that.

Time to loss of brain function and activity during circulatory arrest reports findings of a literature review published in 2016 and many of the reviewed publications were published much earlier than that.

Guideline 6: Minimum Technical Standards for EEG Recording in Suspected Cerebral Death records some details of early standards, practices and literature going back at least to the 1960s. It is focused on use of EEG to confirm death as opposed to EEG recording 'of a dying human brain', but it is inconceivable, given the intense interest at the time, that there were no EEG recordings around the time of death prior to the recording reported in 2022.

This is not to suggest that there was nothing novel in the reported findings, but the 'first-ever recording' in the headline is, I think, sensationalist misrepresentation.