With the suspect caught and Boston breathing a sigh of relief, President Obama thanked police, praised the city, and a promised to investigate what motivated two brothers to allegedly turn to mass violence.
"Obviously, tonight there are still many unanswered questions -- among them: Why did these young men who grew up in our country and studied here as part of our communities and our country resort to such violence?" Obama said from the White House press briefing room late Friday night.
"How did they plan and carry out these attacks and did they receive any help?" Obama said. "We will determine what happened. We will investigate any association that these terrorists may have had, and we'll continue to do whatever we have to do to keep our people safe."
Authorities apprehended "Suspect No. 2" in the Boston Marathon bombings, Dzhokhar Tsarnaev, in suburban Boston Friday night after a days-long manhunt that left one police officer dead at the MIT campus.
Tsarnaev's brother, the other suspect, was also killed.
The president thanked law enforcement officers, offered condolences for each victim of the Boston marathon bombings and for the family of Sean Collier, the Massachusetts Institute of Technology police officer shot and killed at the beginning of the wave of violence in Boston that began Thursday night.
Obama also cautioned against rushing to judgment -- perhaps a not-so-subtle reference to speculation that the brothers, ethnic Chechens from Kyrgyzstan, received help or training from someone outside the U.S.
"When a tragedy like this happens, with public safety at risk and the stakes so high, it's important that we do this right," Obama said. "That's why we have investigations. That's why we gather the facts. That's why we have courts. That's why we take care not to rush to judgment about the motives of these individuals, [and] certainly not about entire groups of people."
Praising the people of Boston for "refus[ing] to be intimidated" and Americans for refusing "to be terrorized," Obama gave a nod to the long week of violence that included a ricin-laced letter mailed to Obama, multiple bomb scares, and a massive explosion at a fertilizer plant in West, Texas, that killed at least 14 and injured 200.
"All in all, this has been a tough week," Obama said. "As president, I'm confident that we have the courage and the resilience and the spirit to overcome these challenges and go forward as one nation, under God, indivisible, with liberty and justice for all."