Chad Schieber, who collapsed while running on the city's South Side, had a mitral valve prolapse and did not die from the heat, the medical examiner's office said Monday.
Many of the runners in the LaSalle Bank Chicago Marathon say they were promised extra hydration along the course, but they didn't get it, reports Pamela Jones of CBS station WBBM-TV.
"There was no where near enough water for how hot it was," runner Doug Deram said.
Debilitating weather plagued this year's 30th annual run, forcing organizers to shut down the race in which the officer died and dozens of other runners were hospitalized, including two who remained in critical condition early Monday.
The 35-year-old Schieber, from Midland, Mich., was pronounced dead shortly before 1 p.m. Sunday at a hospital.
Several other people collapsed, and at least two remained in critical condition Monday, as record heat and smothering humidity forced race organizers to shut down the course midway through the event.
Shawn Platt, senior vice president of LaSalle Bank, the marathon's sponsor, said it was, "Obviously very sad news, and our thoughts and prayers are with the individual's family."
The father of three was just named police officer of the year in his hometown of Midland, reports WBBM's Katie McCall. His wife and brother were also running the marathon, but had no idea he had died until they went back to their hotel.
It was his first marathon.
Marathon deaths are not unusual, occurring in about 1 in 50,000 runners. The last death in the Chicago Marathon was in 2003.
Race director Carey Pinkowski said organizers closed the race on concerns that emergency medical personnel wouldn't be able to keep up with heat-related injuries as the weather turned more cruel.
"We were seeing a high rate of people that were struggling," Pinkowski said. "If you were out there at 1 o'clock, it was a hot sun. It was like a summer day, it was just a brutally hot day."
At least 49 people were taken to hospitals, while another 250 were treated onsite, many for heat-related ailments. About 10,000 of the 45,000 registered runners never even showed up for the race, while another 10,934 started but didn't finish, officials said.
"Towards the end of the race, it looked like a war zone to me, actually," said runner Brian Tannebaum. "I saw a lot of runners just being carried off. I heard people calling out 'medic, we need a medic.'"
By 10 a.m., temperatures had already reached a race-record of 88 degrees. The previous marathon record of 84 degrees was set in 1979. The high heat index prompted organizers to stop the race at 11:30 a.m., about 3½ hours into the run. Runners who hadn't reached the halfway point were diverted to the start and finish area, while those on the second half of the course were advised to drop out, walk or board cooling buses, Platt said.
He and other organizers acknowledged that not all runners heeded the warnings, and many continued. Helicopters hovered over the race course while police officers shouted through a bullhorn and warned runners to slow down and walk.
"I actually had to take a dirty cup from the ground to get some water or I'd be dehydrated. It was horrible," said runner Gerri Korblut.
"We would have to fight through the crowds to get someone to fill our water for us," added Mary Rogers.
But some runners said they understood the difficulty of keeping the huge crowds healthy in such heat.
"I think that they tried the best they could, runner Janice Karosas told WBBM. "Yeah, they ran out of water, but people were squirting water on their heads and that's how they ran out. You see people taking two or three and they were just trying to be cool."
Pinkowski said he was confident there were enough fluids at the race's 15 aid stations, but he said race officials would "go back and take a real hard look at it."
Lori Kaufman, a runner from St. Louis, said she was told to start walking at mile 14. She said the fire department turned on hydrants to hose people down along the course. She also said she didn't have enough water and Gatorade.
"We had a lot of spectators just handing us bottles of water, which helped a lot," Kaufman said. "Every medic station that we passed was full of people. I mean they were not doing well."
The decision to end the race early was one of many unusual moments Sunday that began when Kenyan Patrick Ivuti won the muggy marathon in the closest finish in race history, edging Jaouad Gharib.
In the women's race, Ethiopian Berhane Adere rallied with a come-from-behind final sprint to defend her title.