Getting nursed back to health, however, had one upside. While recovering at Spaulding Rehabilitation Hospital, Costello met and fell in love with traveling nurse Krista D’Agostino.
Eight months later, Costello popped the question while the two were on a 10-day cruise to Europe organized for survivors of the Boston Marathon attack.
According to Boston magazine, Costello posted the announcement on his Facebook page, which has since been unavailable to the public.
"April 15 was one of the worst days of my life," he wrote. "I soon wondered why and for what reason this has happened. I now realized why I was involved in the tragedy. It was to meet my best friend, and the love of my life.
Costello had written on his Facebook page that he fell in love with the nurse after “sharing a handful of conversations” and seeing her inner and outer beauty.
“I somehow convinced her to attend a benefit with me, which turned into a few dates, which turned into a few inseparable months,” he wrote.
D’Agostino reportedly said yes to Costello’s proposal while the two were traveling around Lyon, France. They are expected to return to the U.S. on Dec. 21.
Several people who said they know the couple expressed excitement over the announcement.
Spaulding Rehabilitation Hospital spokesman Tim Sullivan told the Los Angeles Times that hospital staffers are buzzing about the news.
"Everyone who worked on the floor loves the story," he said. "People keep asking each other, 'Oh did you hear about it?'"
Sullivan said people call the engagement "wonderful."
"We take a lot of joy that they [Boston Marathon bombing survivors] can have positive experiences happen to them," he said. "Because they really do deserve it."