Testifying as the final witness, former premier Dalton McGuinty said he found it "shocking" to learn rescuers had given up because the unstable mall was too dangerous.
"If that's my daughter in that building, or my mother, or my fiancee, I want no stone left unturned," McGuinty explained.
"I had no reason to believe that the rescue effort would have continued without my intervention."
The collapse of the Algo Centre Mall on June 23, 2012, killed Doloris Perizzolo, 74, and Lucie Aylwin, 37. While an autopsy showed Perizzolo died quickly, Aylwin is believed to have lived longer.
Whether a more robust effort might have saved her will likely never be known, but angry relatives and residents were dismayed rescuers had decided to pack it in.
"People were upset, angry, hurt. It was a bad scene," McGuinty said.
He called it "unacceptable" to give up even if the possibility someone could be saved was remote.
In an evening telephone call two days after the collapse, Staff Insp. Bill Neadles, the head of the heavy urban search and rescue team, told McGuinty there was no way to go into the building given the danger.
In response, McGuinty said he pushed the makings of a fraught and risky Plan B: Try to get at the victims by bringing in heavy equipment and dismantling the building from the outside.
The ex-premier said he did not order resumption of the rescue, which turned out to be futile, but simply impressed on Neadles to do any and everything possible.
"My concern was to do nothing would be for death to ensue," McGuinty testified. "We had to try to do something."
He also called Prime Minister Stephen Harper to ask if the military could be deployed if needed, and was told it could be, the inquiry heard.
McGuinty, only the third Ontario premier or former premier to testify at a public inquiry in about 70 years, was the last of 125 witnesses to testify over 117 days during the evidentiary hearings, which began March 4.
"All my political instincts told me that this warranted a thorough and thoughtful review," he said of his decision to call the inquiry.
"A search had been on, and then it was off."
He noted the inquiry is also addressing concerns about the availability of heavy equipment and expertise, especially in more remote areas.
One resident, Roger Hachey, said he thought McGuinty had come across as "really real" and "genuine."
Hachey also said he was glad the hearings were over, and was looking forward to the recommendations Commissioner Paul Belanger will make, likely next March, based on 28,900 pages of transcripts and 11,000 exhibits.
"People didn't do their jobs, provincially, municipally," Hachey said.
"That's one thing that has to change: if you're in position of responsibility, do your job."
The inquiry previously heard how the poorly designed and built mall — a critical hub in the town of 13,000 — leaked from the get-go. No one, however, tackled the expensive-to-fix problem substantively and decades of water and salt penetration caused extreme rusting.
Ultimately, a single weld gave way, and part of the rooftop parking deck came crashing down.
Belanger will still hear from expert panels in November and December as he forges his recommendations.
"The scars left behind from the deaths of Doloris Perizzolo and Lucie Aylwin will likely never be erased," Belanger said in his closing comments.
"But still, one cannot help but admire the spirit of this community."
Darrin Latulippe, Perizzolo's son-in-law, who has been fiercely critical of the way the rescue was handled and relatives were kept informed about what was going on, expressed gratitude for McGuinty's participation.
He also thanked Belanger for "maintaining the dignity and respect of our lost loved ones."
Note to readers: This is a corrected story. An earlier version contained the wrong first name for inquiry commissioner Paul Belanger.