A man who finished running the Boston Marathon seconds before a bomb exploded near the finishing line on Monday was also one of the witnesses of the Texas fertiliser plant disaster on Wednesday.

Joe Berti, 43, said: "I was just like, 'I can't believe this!' I just want to get out of here and get away from all these explosions."

Berti said he was fortunate as he left both tragedies unscathed; members of his running group and his wife, who was closer to the Boston explosion than he was, were also unhurt.

"It's a miracle," he said in an interview with the Associated Press. "Not only do I not feel unlucky, but I feel blessed that my wife … did not have a scratch."

Monday's bombings in Boston killed three people and left more than 180 wounded. Wednesday's explosion in West, Texas, killed at least five people and injured more than 160.

"We're grateful that God has been merciful to us," said Berti's wife, Amy. "We are just praying for the people who were so much less fortunate than we were."

Berti ran the marathon to raise money for a charity that helps children with rare or undiagnosed disorders. "I had just run to the finish line and like 30 seconds later I heard the first explosion, and then turned around and saw the smoke," he said. "I knew immediately that it was a bomb ... Then the second explosion occurred and I saw a wave of people running."

He said he was so exhausted he could not run anymore and was worried about getting caught in a stampede and the fate of members of his running group and his wife.

Amy Berti and a friend had just taken a picture of Joe and was heading to the finish line to find him when the bomb went off. They were both hit by shrapnel. Amy was uninjured, but her friend was bruised.

However, a woman next to Amy had her leg torn off from the knee down and lost all the fingers on her left hand. Amy Berti went to get help and, once that woman was being cared for, Amy's frantic search for her husband began.

The Bertis eventually reunited and they left Boston on Tuesday morning and returned to Texas.

Joe Berti went back to work and was returning home from a meeting in Dallas when he saw – and felt – his second explosion in two days.

"You've got to be kidding!" he remembers thinking. He described the giant fireball as a massive force that shook his car. "My next reaction was to get out of there because something fell on the top of my car – some debris or something fell from the sky," he said.

As black smoke billowed over the highway in front of him, Berti held his breath and drove on and was able to reach his wife.

"I'm like, 'Honey, what is with your luck? Why are you in all of these places?" she said. "We need to keep him moving. Maybe he just needs to stand in an open field."