UPDATE: Urbandale Man Who Checked Marathon Off Bucket List Recalls 'Unreal, Crazy Situation'

Updated at 7:06 p.m.

Tom Mertz of Urbandale had a great day Monday before tragedy marred the 117th running of the Boston Marathon.

“It was an unbelievable experience,” said Mertz, a project manager for Monsanto in Ankeny. “it was really perfect weather, a great day.”

And then it wasn’t.

From the 33rd floor of their room in Westin Copley Place Boston Hotel on Huntington Avenue, Mertz and his wife watched the carnage unfold after two explosions brought the celebratory atmosphere of the marathon to an abrupt end. CNN is reporting two people were killed and 111 were injured in the blasts, which the FBI is treating as a terrorist attack.

Mertz said he heard what sounded like an M-80 firecracker going off in a garbage can, then another.

“When the second one went off, we could see windows blown out and that it was going downhill in a hurry,” he said. “People were losing their legs in the blast or being killed. ... It’s just unreal, a crazy situation.”

News conferences were being held at their hotel, giving the Mertzes reassurance that their hotel was safe while others around them remained on lockdown.

Running the marathon was “one of those bucket list things,” Mertz, 40, said. “It’s been a goal for a number of years. ... Right up until this happened, it was just a spectacular storybook experience, one for the record.”

Earlier, Patch reported:

Kimberly Baeth of Urbandale describes the scene near the finish line of the Boston Marathon as something from a horror movie after at least two explosions rocked the site Monday afternoon.

Baeth and her husband, Kevin, were at the marathon, she was less than a mile from the finish when the bombs detonated. She told Urbandale Patch that Kevin was waiting for her to complete the race only 100 yards from the bomb site.

The couple is uninjured, but she describes the scene as "blood everywhere. A total sense of shock at first, and so many scared people trying to find their lived ones," Kimberly wrote in a Facebook message.

A pair of blasts near the finish line at the marathon on Monday afternoon killed two people and injured at least 50 people, a CNN producer at the scene said. The blasts occurred a few seconds apart, shrouding downtown Boston's Copley Square in smoke. The explosions occurred about 2:45 p.m., about an hour after the first runners had crossed the finish line, CNN said.

"We were really lucky and certainly some people were not," Kevin told Urbandale Patch by phone. "If that's all the fatalities, it will be amazing."

According to BackBay.Patch.com, CBS-Boston is reporting federal officials have surveillance images of a man dropping backbacks into trashcans.

The marathon's website says 158 Iowans were registered to take part in the race.

Boston Police have worked to update the public through their Twitter account. Officers are asking anyone with video of the finish line to send it to the department.

What do you think of such a tragedy at an event that celebrates health and strength? Share your thoughts in a blog on Urbandale Patch.

When she was about .3 kilometers from the finish, Kimberly said she heard a big bang and "all the runners were like 'What was that?' We thought maybe a cannon misfired and saw smoke rise up."

Then a bus blocked the street and the race stopped. Kimberly didn't have a cell phone with her to contact Kevin, who was waiting for her near the finish line.

"I knew Kevin would be right there where it went off," she said.

Runners were detained for about 45 minutes before they were allowed to rejoin family and friends, Kimberly said.

"It was smoky, it was people running everywhere, people were crying. … I couldn't find Kevin and I was really, really worried that he was one of the hurt ones."

When she returned to their hotel, Kimberly found Kevin unharmed and waiting for her in the lobby.

He was across the street from the first explosion. "Once I looked down and saw the smoke I knew there was something serious going on. It wasn't a cannon and it was terrorist activity," Kevin said.

When the second explosion went off people started to panic. "It was somewhat controlled mayhem. It wasn't a mad dash but it was 'Oh my gosh, you could die, you got to get out of there'."

Kevin said his instinct was to get away from every trash can, because he kne that's typically where bombs are placed.

Because he could track Kimberly's finish time through the marathon website, and she wasn't listed, he knew she was safe.

Kevin is an employee of Wells Fargo Home Mortgage in West Des Moines, while Kimberly runs Golden Openings, which coordinates business events and groundbreakings.

When asked if they will go back to Boston, he said, "Absolutely. We live in a world where terrorism is unfortunately a part of our lives. I'm of the belief that you can't let terrorists dictate what you do."