The Boston marathon attracts more than a half million spectators and 20,000 runners every year from all over the world.  Many of those runners are from Houston. 

"I was able to get through to my son who's watching, so I knew they were okay," said Karen Bookstaff.  Her husband Howard ran the Boston marathon on Monday and their 24-year-old son, Evan, watched. 

Bookstaff had a hard time getting in touch with them at first because the phone lines were jammed and no calls were coming in or going out of Boston.

Eventually she heard from them and learned that her son hadn't been too far from where the first bomb went off. 

Her husband Howard told Local 2 over the phone from Boston that the grandstands, where people go to watch the finish line, were hit the hardest. 

"That's one of the best viewing areas by the finish line," Bookstaff said.  "it was packed."

"I got a text about the bombing and I was shocked," said Sean Wade, a Houston running coach who heads up a group called The Kenyan Way. 

Wade trains runners to qualify for the Boston marathon and couldn't get a hold of some for several hours Monday afternoon. 

"This year we may have had fifty runners in Boston.  So far 35 have checked in," he said.  "We know of a couple of runners who finished about the time the bomb went off.  We haven't heard from them yet. We're making some calls and trying to make sure they're okay."

Wade's group quickly started an email chain and the messages started pouring in.  Everyone was accounted for and safe. 

"You wouldn't ever think to worry about this for a marathon," Wade said.