@hightor,
It is still unclear where Trump was infected with the corona virus. The President has had numerous daily appointments over the past weeks.
But one of these events is: the nomination of Amy Coney Barrett as a Supreme Court judge. Trump had nominated the lawyer for the highest judicial office last Saturday, and since then at least seven participants have tested positive for the corona virus.
Photos showed guests standing together and hugging each other without masks and minimum distance. The nomination itself took place in the Rose Garden of the White House, i.e. outside. According to media reports, the guests also stayed indoors during the subsequent reception.
Besides the accumulation of positive infected persons, the time lapse is also striking. Corona-infected people develop symptoms on average five days after infection. After the nomination on Saturday, symptoms could have been expected on Thursday - which fits in quite well with the timing of Trump, who announced his infection on Friday.
Actual evidence of Trump's chain of infection has not yet been found. For example, he could have contracted the disease from Hope Hicks, with whom he is in close contact, and who tested positive on Wednesday. Hicks was not present when Barrett was nominated in the Rose Garden.
A completely different source of infection is also conceivable.