Oberg and Weber athletic trainer Joel Bass competed in Monday's annual marathon. They were two of the 354 Utahns who had entered the race.
Bass completed his run 40 minutes before Oberg and was waiting with Oberg's wife, Lynette.
They were a half block away and had just ducked into a 7-Eleven for chocolate milk when they felt the explosions. Bass said the plume of smoke rose six stories into the air.
"They had wheelchairs for the racers and they were bringing [injured] people in on them," a shaken Lynette Oberg said. "There was one lady on a stretcher and they were using chest compression."
Oberg said the second explosion went off about five seconds after the first.
"People started running," she said. "People announcing the racers, they started running."
Oberg said the gates used to keep spectators from running onto the course funneled the crowd away from the bomb area. Craig Oberg then noticed armed military personnel on a nearby roof.
"There are so many people here. Ambulances and SWAT. Medical and military people everywhere," Bass said. "There were 10 or 12 ambulances just on the block I was on."
Utah Gov. Gary Herbert's daughter, Kim Cahoon, ran the marathon but finished about an hour before the blasts and had left the race.
"As grateful as I am that my daughter is safe and was not nearby when the bombs went off, I am deeply shocked and saddened by this tragedy," Herbert said. "This hits home, not only because my daughter was there, but also because many other Utahns participated in the race today."
Based upon finish times, about 50 Utah runners were in the vicinity of the finish line when the blast went off, either just finishing or nearing the race's conclusion.
Julie Isaacson of Salt Lake City was running the marathon for a second time and her husband, Scott, was waiting about a half mile from the finish line.
When she ran past, he jogged alongside her temporarily until she ran on ahead of him.
Julie crossed the finish line and sat down to catch her breath when she heard and felt "a thunderous explosion."
"My back was initially turned and I was scared and shocked and turned around and thought, 'Is this a cannon going off?'," she said.
There was pandemonium, but runners were still filing across the finish line and volunteers were still handing out blankets and water. Scott Isaacson was moving toward the finish line when he heard and saw the first blast near the finish line, the area he knew his wife would be.
"Then a couple seconds later, the second one happened right across the street from us," he said.
"It was the same huge, loud bang and you could see it and hear it," he said. "We immediately saw people go down, bloodied and, unfortunately, I think dead, right across the street from us."
"I would describe it as chaotic and surreal. You just don't know what to feel, but immediately it was obvious what it was. I don't think there was any confusion from the first second what was going on," he said.
Caryn Willardsen of Salt Lake City said the sound of the second blast hurt her ears and the ground felt like it moved.
"I could see that legs were missing. There was a lot of blood. People were dragging their loved ones or whoever, their companions, farther away [from the blast]. One man tried to pick up a girlfriend wife or mother, but he picked her up and was trying to walk her out in the road away [from the blast] and her leg was not connected, it was dangling, and had to lay her down in the middle of the road," Willardsen said. "There was one woman who was on fire, people were screaming that her pants were on fire and a police officer came and pulled her pants off and all the way down the side of her leg was charred."
Wayne Cannon, a Salt Lake phyisican who ran the race with his wife Gwen, called the emergency medical response "amazing. "They had help there within a minute or two. There was chaos everywhere."
The Cannons were about 400 yards from the finish line when the first blast occurred and immediately left the course.
Celestia Carson of Salt Lake City also left the course before finishing her first Boston Marathon.
"I was a little slow today," she said. "Maybe that was a good thing."
Althea Luhm, a junior at Emerson College near the Boston Common, remained in her Cambridge home. Luhm described an increasingly stressful atmosphere in the Boston area.
"Even though everyone is calm, it's a lot to take in," she said. "We're becoming more and more worried. It's like, we're so thankful we're here. I work downtown and am thankful I didn't take that extra shift."
Reporters Christopher Kamrani, Robert Gehrke and Aaron Falk contributed to this story.
Join us for a live Trib Talk chat about Saturday's Salt Lake City Marathon the nation's first after Boston Tuesday at 11 a.m. at sltrib.com. Host Jennifer Napier-Pearce will lead a discussion featuring BYU cross country coach Ed Eyestone, eight-time marathon participant Andy Hortin and others.
Submit your questions at any time in the comments, or via hashtag #tribtalk on Twitter or Google+.
Click here for Google's person finder for the Boston Marathon explosion.