Liz Norden of suburban Wakefield told the Boston Globe that two of her sons, both in their 30s, each had a leg amputated from the knee down.
President Obama, speaking on national television Monday night from the White House, assured the nation "we will find who did this and we will find out why they did this. Any responsible individuals, any responsible groups will feel the full weight of justice."
Investigators said they did not know if the bombings were connected in any way to the marathon being run on Patriots Day, a state holiday in Massachusetts to commemorate the start of the Revolutionary War with the battles of Lexington and Concord more than 235 years ago. It was also noted that Monday was the deadline for filing federal taxes.
The marathon is an iconic Boston event, attracting elite runners from across the world. Lelisa Desisa of Ethiopia won the men's division Monday, and Rita Jeptoo of Kenya the women's division. Both finished more than two hours before the bombing.
Details for this story were provided by the FBI, Massachusetts State Police and the Boston Police Department.