The exact details may never be known, but Mr. Hackman, 95 with advanced Alzheimer's, was alone for about a week after his wife and sole caregiver died.
Mr. Hackman had Alzheimer's, which contributed to his death from heart disease, New Mexico's chief medical examiner said. His wife, Betsy Arakawa, died before him from a respiratory illness.
President Trump, in an early February call, challenged the border treaty between the two countries and told Justin Trudeau he didn't like their shared water agreements.
President Trump's fixation reinvigorated the debate over the role of the federal government in education, and created a powerful point of unity between the factions of his party.
Mr. Hackman's body was found inside his home, along with those of his wife and a dog. The sheriff in Santa Fe, N.M., said it was likely Mr. Hackman died on Feb. 17, nine days before the bodies were discovered.