The two suspects of the bombings, in which three people were killed and more than 180 others were injured, were brothers of Chechen-origin.
While the elder brother was shot dead on Thursday night, the younger, 19, was arrested from a Boston neighborhood today where he was hiding in a boat parked in the backyard of a house.
As the nation heaved a sigh of relief on the news of the arrest of the second suspect, Obama was quick to address the nation, in which he congratulated the law enforcement agencies for this, but asserted that he will find out the motive behind such an attack.
"Obviously, tonight there are still many unanswered questions. Among them, why did young men who grew up and studied here, as part of our communities and our country, resort to such violence? How did they plan and carry out these attacks, and did they receive any help? The families of those killed so senselessly deserve answers," Obama said.
"The wounded, some of whom now have to learn how to stand and walk and live again, deserve answers," he said.
As such, Obama said, he has instructed the FBI and the Department of Homeland Security and the intelligence community to continue to deploy all the necessary resources to support the investigation, to collect intelligence, and to protect the citizens.
"We will determine what happened. We will investigate any associations that these terrorists may have had. And we'll continue to do whatever we have to do to keep our people safe," Obama said.
"One thing we do know is that whatever hateful agenda drove these men to such heinous acts will not - cannot - prevail. Whatever they thought they could ultimately achieve, they've already failed. They failed because the people of Boston refused to be intimidated," he said.
"They failed because, as Americans, we refused to be terrorised. They failed because we will not waver from the character and the compassion and the values that define us as a country. Nor will we break the bonds that hold us together as Americans," Obama said.
"That American spirit includes staying true to the unity and diversity that makes us strong - like no other nation in the world. In this age of instant reporting and tweets and blogs, there's a temptation to latch on to any bit of information, sometimes to jump to conclusions," he said.
"But when a tragedy like this happens, with public safety at risk and the stakes so high, it's important that we do this right. That's why we have investigations. That's why we relentlessly gather the facts. That's why we have courts," the US President said.
"And that's why we take care not to rush to judgment - not about the motivations of these individuals; certainly not about entire groups of people," he said.
"After all, one of the things that makes America the greatest nation on Earth, but also, one of the things that makes Boston such a great city, is that we welcome people from all around the world - people of every faith, every ethnicity, from every corner of the globe," Obama said.
"So as we continue to learn more about why and how this tragedy happened, let's make sure that we sustain that spirit," he added.