Gunfire, explosions after man kills MIT police officer

Gunfire and explosions erupted in streets close to the prestigious Massachusetts Institute of Technology on Friday after a police officer was shot dead there, witnesses said. Local media said one person may have been shot in the incidents as heavily armed police launched a major manhunt following the killing on the MIT campus near the US city of Boston. The explosions and gunfire were heard in the Watertown district north of the university. "There were blasts, it could have been grenades," local resident Adam Brown told AFP. The NBC-WJAR channel later showed film of a man lying on the ground in a street in the town and surrounded by police. Two hours earlier, a gunman shot dead an MIT campus policeman. MIT is in Cambridge, Massachusetts, just across the Charles River from Boston, where three people were killed and 180 injured in a double bomb attack on the city's marathon on Monday. Authorities made no immediate link between the two incidents. Earlier Thursday the FBI had released pictures and video of two men suspected of planting the Boston marathon bombs, appealing for help to identify the pair who were carrying large backpacks. Investigators consider the suspects to be "armed and extremely dangerous," said Rick DesLauriers, Federal Bureau of Investigation (FBI) chief in Boston, warning that no-one should approach them. Authorities stepped up checks on the Canadian border as they released the images. And the clamor to see the pictures was so great that the FBI's website, www.fbi.gov, crashed minutes later. Two bombs were placed around the marathon finish line on Monday, spraying nails, ball bearings and other metal fragments into the crowds, many of whom suffered horrific injuries. "Identifying and locating those responsible is now our highest priority," DesLauriers said. "The images from Monday are indelible and the horror of that day will remain with us forever."