On Tuesday (local time), Mr Monroy again escaped with his life, but for the first time there were bodies strewn about as he rushed to rescue his family from the scenes of carnage emerging from shattered stalls that had bustled with Christmas cheer moments earlier.
At least 32 people died and dozens were injured when the huge fireworks bazaar on the northern fringe of Mexico City exploded in a dazzling array of lethal pyrotechnics that razed the marketplace to a blasted plain of smoking rubble.
In little over a decade, the country's most celebrated fireworks market in Tultepec has blown up three times, with the latest massive blast raising serious questions about why the festive public was again exposed to such deadly risks.
"This was the biggest and the worst," 41-year-old Mr Monroy said after his last escape.
"It was really loud, like a bomb. Lots of people were running and looking for help, and those we could get out, we got out."
Alan Jesus Chavez, a local medical student who rushed to the scene as the blasts went off and the market stalls blazed, worked to pull people out of the burning ruins.
While handing out milk and water, a woman came to his side to ask him to free her baby, who was trapped under rubble.
"But when we got everything off and found the baby, it was already dead," said Mr Chavez.
The Government has yet to say what sparked the tragedy, noting only that there were six separate blasts. Federal investigators pored through the wreckage for clues on Wednesday.
Local resident Ivan Perez, 23, whose girlfriend works at the market, said there was a rumour that the explosions began when a woman accidentally dropped a "brujita", a kind of banger.
Mr Perez said that due to the economic importance of the bazaar, bribes were sometimes paid to sell fireworks not permitted by official regulations.
But after the third tragedy in just over a decade, the market's prospects looked grim, he added.
"I don't think it will get back on its feet," he said.