"At first I thought it was a salute," Ekelberg told Norwegian broadcaster NRK. "But then I saw the emergency vehicles coming in. Fire trucks, ambulances. Then we realized something wasn't right."
Tracy Eaves had just crossed the finish line moments earlier to finish her 39th marathon, collected her medal and called her husband back in Niles, Mich., when she felt and heard "this huge shaking boom."
Eaves told her husband she thought it was a celebratory cannon blast. After the second blast, she started to panic.
Race officials quickly ushered her and other runners from the scene. She eventually made her way back to her hotel.
"You're so happy and excited to finish. You're ecstatic. You get your medal. You get your Gatorade and — boom."