WATERTOWN, Mass. (AP) — The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the run, authorities said Friday as thousands of officers swarmed the streets in a manhunt that paralyzed the Boston area. The suspects were identified by law enforcement officials and family members as Dzhokhar and Tamerlan Tsarnaev, ethnic Chechen brothers who had lived in Dagestan, which neighbors Chechnya in southern Russia. They had been in the U.S. for about a decade and lived near Boston, an uncle said. Tamerlan Tsarnaev, a 26-year-old who had been known to the FBI as Suspect No. 1 and was seen in surveillance footage in a black baseball cap, was killed overnight, officials said. His brother, a 19-year-old college student who was dubbed Suspect No. 2 and was seen wearing a white, backward baseball cap in the images from Monday's deadly bombing at the marathon finish line — escaped. Their uncle in Maryland, Ruslan Tsarni, pleaded on live television: "Dzhokhar, if you are alive, turn yourself in and ask for forgiveness." Authorities in Boston suspended all mass transit and warned close to 1 million people in the entire city and some of its suburbs to stay indoors as the hunt for Suspect No. 2 went on. Businesses were asked not to open. People waiting at bus and subway stops were told to go home. From Watertown to Cambridge, police SWAT teams, sharpshooters and FBI agents surrounded various buildings as police helicopters buzzed overhead and armored vehicles rumbled through the streets. Authorities also searched trains. "We believe this man to be a terrorist," said Boston Police Commissioner Ed Davis. "We believe this to be a man who's come here to kill people." The bombings on Monday killed three people and wounded more than 180 others, tearing off limbs in a spray of shrapnel and instantly raising the specter of another terrorist attack on U.S. soil. Chechnya is the home of an Islamic insurgency that has carried out deadly bombings in Russia and the region, but its militants have never been known to export violence to the West.