Amazon, which has its highest employment during the holiday shopping season, said the tornado formed at the site’s parking lot.Nearly every day as Christmas nears, Amazon’s share of online sales typically rises, as customers turn to the e-commerce giant to quickly deliver packages. To make that happen, Amazon hires hundreds of thousands of additional workers, both full-time employees and contractors, and runs its operations at full tilt.One of them, Alonzo Harris, drove his cargo van into Amazon’s delivery depot in Edwardsville, Ill., after 8 p.m. on Friday after a full day delivering packages north of St. Louis. Suddenly, an alarm blared on his work phone. Someone yelled that this was not a drill. Mr. Harris, 44, ran into a shelter on Amazon’s site and heard a loud roar.“I felt like the floor was coming off the ground,” he said. “I felt the wind blowing and saw debris flying everywhere, and people started screaming and hollering and the lights went out.”One of the tornadoes that roared through Kentucky, Arkansas, Illinois and other states on Friday had plowed straight into Amazon’s delivery station in Edwardsville. The toll was grim: Six people died, with 45 making it out alive, according to the Illinois governor, J.B. Pritzker.At least six people died after a tornado tore through an Amazon warehouse in Edwardsville, Ill., on Friday.MaxarOn Sunday, the authorities said that there were no additional reports of missing people but that search efforts were continuing. It was initially unclear how many people had been at Amazon’s site and what safety measures could have been taken to minimize the loss of life. The tornado was ferocious, ripping off the building’s roof. Two of the structure’s 40-foot-high concrete walls collapsed.The tornado coincided with a peak in the company’s work force. Americans’ reliance on Amazon soon turned the deaths at the delivery depot into a focus of the public as the tornadoes’ toll became clear over the weekend.At a church service on Sunday at Thrive Church in Granite City, Ill., about 15 miles from the destroyed Amazon site, clergy and congregants tried to make sense of the disaster and the company’s response.“It’s not lost on me, Lord, that this was an Amazon warehouse, and I, like so many other people in this country, get irritated if I can’t get my Christmas gifts in three days from Amazon,” Sharon Autenrieth, the pastor, said during the service.That logistical peak also complicated the rescue effort in Edwardsville. The more than 250,000 drivers like Mr. Harris who fuel Amazon’s delivery network do not work directly for the company but instead are employed by over 3,000 contractor companies. On Saturday, Mike Fillback, the police chief in Edwardsville, said the authorities had “challenges” in knowing “how many people we actually had at that facility at the time because it’s not a set staff.”Only seven people at Amazon’s site were full-time employees, said a Madison County commissioner who declined to give his name. He said most were delivery drivers in their 20s who work as contractors.The delivery center sits in a flat industrial expanse with low-slung warehouses, parked semi-trucks and muddy fields a few miles east of St. Louis and the Mississippi River. An Amazon fulfillment center almost directly across the street from the delivery station was largely untouched. On the front windows there, next to images of snowflakes and Christmas trees, were the words “Peak 2021” and “Our Time To Shine.”On Sunday, Kelly Nantel, an Amazon spokeswoman, said about 190 people worked at the delivery station across all of its shifts but declined to comment on how many were full-time workers. She said the tornado formed in the parking lot, hit and then dissipated.The tornado struck at the end of a shift, as drivers returned their vans, unloaded items and headed home. Contract drivers are not required to clock into the building, Ms. Nantel said.Workers there sheltered in two places, she said, and one of those areas was directly struck. These areas are typically fortified, though it was unclear if they were built to withstand a direct tornado strike. Based on preliminary interviews, Ms. Nantel added, the company calculated that about 11 minutes lapsed between the first warning of a tornado and when it hit the delivery station.The six victims ranged in age from 26 to 62 years old, the Edwardsville police department said on Sunday.Amazon’s model of using contractors is part of a huge push that the company started in 2018 to expand its own deliveries, rather than rely solely on shipping companies like UPS. The company built a network of delivery stations, like the one Edwardsville, which are typically cavernous, single-story buildings.Unlike Amazon’s massive, multistory fulfillment centers where it stores inventory and packs items into individual packages, the delivery stations employ fewer people. Amazon employees sort packages for each delivery route in one area. Then, drivers working for contractors bring vans into another area, where the packages are rolled over in carts, loaded into the vans and driven out.Amazon had about 70 delivery stations in the United States in 2017 and now has almost 600, with more planned, according to the industry consultant MWPVL International. Globally, the company delivers more than half of its own packages, and as much a three-quarters of its packages in the United States.Most drivers work for other companies under a program called Delivery Service Partners. Amazon has said the contracting arrangement helps support small businesses that can hire in their communities. But industry consultants and Amazon employees directly involved in the program have said it lets the company avoid liability for accidents and other risks, and limits labor organizing in a heavily unionized industry.Sucharita Kodali, an analyst at Forrester Research, said that while the holiday season is critical for all retailers, it is particularly intense for Amazon. “They promise these delivery dates, so they are likely to experience the most last-minute purchases,” she said.The Edwardsville delivery station, which Amazon calls DLI4, opened last year and had room for 60 vans at once, according to planning documents.On Friday, a tornado warning was in effect for Edwardsville as of 8:06 p.m., according to the National Weather Service. At 8:27 p.m., the county emergency management agency reported a partial roof collapse at Amazon’s delivery depot and that people were trapped inside.Aerial footage of the wreckage showed dozens of vans, many of which had Amazon’s logo, underneath the rubble. Some of the vans were U-Hauls, which the contractors sometimes rent to serve demand during busy periods.Carla Cope and her husband, said their son, Clayton Cope, 29, was a maintenance mechanic contracting for Amazon. They spoke to him by phone on Friday night when he was at work, they said, and he assured them that he and other workers were on their way to the tornado shelter on site.About 10 minutes later, the tornado struck. The Copes tried numerous times to reach their son again by phone. They eventually drove to the warehouse from their home in Brighton, Ill., a half-hour away.“When we pulled up to the building it was pretty devastating,” Ms. Cope said. “There were trucks and rescue vehicles everywhere, a lot of chaos.”When her husband saw the damage, he immediately feared the worst, Ms. Cope said. Mr. Cope works the same job as a maintenance mechanic that their son did, splitting the night shifts except on Wednesdays when the two work together. He knew that their son was likely to have been in the part of the building that collapsed, she said.The couple waited at the building until 4:30 a.m., when officials informed them that they had recovered their son’s body.“There’s just really no words to describe it when they tell you your son’s dead,” said Ms. Cope, her voice cracking. “It’s surreal, unbelievable, devastating.”Mr. Harris, the delivery driver who survived the storm, said that after the tornado passed, he saw a green tornado shelter sign still hanging above Amazon’s shelter.“I doubt anything man-made can withstand Mother Nature’s force,” he said. “I think it was an act of God that our shelter remained secure.”Robert Chiarito More