They were the two twin bombings that sent shock waves through Boston, New England and across the country.
Among those tearing down fences at the finish line of the Boston Marathon to assist the injured were members of the Massachusetts State Police.
On Thursday night, their leader, Col. Timothy Alben, spoke to students and members of the public at Western New England University about that day.
"It was certainly, in some respects, a chaotic day," said Alben.
He called it a controlled chaos.
He explained the department expects the unexpected when it comes to large events like the marathon. It's something they train for.
Alben said that helped authorities to grab control of the situation.
"All of the investments we made in training, education and preparation really came to wish that day for us," said Alben.
In the days following the attacks, a massive manhunt spread through the suburbs of Boston, paralyzing the city.
Alben said officials turned to a new tool, social media, to keep the public informed.
"It was the ability to talk directly and have a two-way conversation with the public to get their input and contribution to the investigation," said Alben.
And with this year's marathon just two months away, Alben said they will once again rely on social media and the public to be their extra set of eyes and ears along the route.
"The public is a partner in all of this," said Alben.
Alben said security preparations for the one-year anniversary are already in place.
"The route will look differently. That's something the public needs to be accustomed to, but it's the new norm now with these events," explained Alben.
Copyright 2014 WSHM (Meredith Corporation). All rights reserved.