John Andrew Satterwhite, 42, and Jerry Mantooth were killed after being overwhelmed by the fumes.
Satterwhite's neighbor Carrie Wilganowski tells Eyewitness News he was the second victim, running to the truck after seeing his boss collapse.
"Andy saw him collapse and Andy thought it might have been a medical emergency, and Andy went immediately to help his boss and immediately collapsed from the fumes," Wilganowski said.
She says his sudden death has left his family and Spring neighborhood devastated.
"We all loved him," Wilganowski said.
Satterwhite was working for Hy-Turf Seeding Company out of Spring.
HISD confirms the company was contracted to get the field ready at Wisdom High School before the school year.
A crew of three, including the company owner, were on location to seed the field.
The Houston Fire Department says the first victim was on the truck, opened the hatch and immediately became overwhelmed by the fumes, falling in.
They say the second victim rushed to his aid and was killed the same way.
Wilganowski says Satterwhite's father told her he was the second victim.
"It didn't surprise me when he said that he went in after his boss to try and save him."
It took six hours for firefighters to recover the two men from inside the barrel of the truck.
They say the fertilizer mixture inside the truck included the highly toxic hydrogen sulfide.
Wilganowski says Satterwhite died just as he was turning his life around.
"Lost about 100 lbs.," Wilganowski said. "Decided he was going to go back to school."
She says something in him had finally found happiness and peace. Then she says his old boss from Hy-Turf Seeding called asking for help.
Wilganowski says she tried to get him to turn it down.
"I said something to him, I said 'Ah, Andy, don't go back, you're going back to school, you don't need to be out in that heat and that stuff. Don't do that.' He said 'No, my boss needs me.'"
She says he'd only been back for six to seven weeks before this unimaginable accident.
Wilganowski had no pictures to share of Andy, saying he was camera shy, but loved gardening, fishing, and his family and neighbors.
"Andy was just a good guy, and I guess that's what I want everybody to know."
He leaves behind his father, mother and brother.
Follow Shelley Childers on Facebook and Twitter.
Follow Brhe Berry on Facebook and Twitter.