Boston bombings: Obama praises officers' sacrifices on Saturday praised the law enforcement officers who worked to search for suspects and secure the Boston area in the aftermath of the . In his weekly video and radio address, Obama praised officers who "worked together throughout the week, often at great risk to themselves, to keep our communities safe." "As a country, we are eternally grateful for the profound sacrifices they make in the line of duty -- sometimes making the ultimate sacrifice to defend the people they've sworn to protect," Obama said. Sean Collier, a campus police officer at MIT, died Thursday after a late-night encounter with the bombing suspects that law enforcement officials called an "assassination." Richard Donohue, an officer with the Massachusetts Bay Transit authority, was severely wounded Thursday night. He underwent surgery on Friday and was listed in stable condition. On the subject of the bombing, the Obama White House kept public remarks to a minimum on Friday. White House Press Secretary Jay Carney canceled his daily briefing, and senior officials deferred to law enforcement officials to talk about the investigation. After the second suspect, Dzhokhar Tsarnaev, 19, was captured late Friday evening, the president spoke in the briefing room, saying, "The families of those killed so senselessly deserve answers." The other suspect, Tamerlan Tsarnaev, 26, was killed in a shootout with police early Friday. On Saturday, Obama praised the "stories of heroism and kindness, resolve and resilience, generosity and love" that he said the nation has witnessed since the Monday bombing. The attack killed three people and injured more than 170 bystanders in the final stretch of the race route. "Ultimately, that's what we'll remember from this week," Obama said. The brave first responders -- police officers, firefighters, EMTs, and National Guard -- who ran toward danger to help their fellow citizens. "If anyone wants to know who we are, what America is, how we respond to evil and terror -- that's it," Obama said.