People gather next to signs reading 'I am Charlie'' in Marseille on January 8, 2015 after 12 people were killed in an attack on a satirical weekly. (ANNE-CHRISTINE POUJOULAT/AFP/Getty Images)

A manhunt is underway in France as police search for the two main suspects in yesterday’s attack on satirical weekly Charlie Hebdo, in which Kalashnikov-wielding gunman opened fire on the newspaper’s offices, killing 12 people. Police identified the two suspects as brothers Said and Chérif Kouachi, 34 and 32, who were known to authorities for previous terrorist activity.

A third suspect, 18-year-old Hamyd Mourad, turned himself in to police Wednesday night and said he drove the getaway car.

French Prime Minister Manuel Valls said Thursday that preventing any further attacks was authorities’ main concern. “We are facing an unprecedented terrorist threat, both internally and externally,” he told a French radio station.

Daily Intel has a detailed primer on the two brothers, who are said to be affiliated with a Yemeni terrorist network. Known to police for their association with radical preacher Farid Benyettou, the brothers reportedly spent time in Syria before returning to France last summer.

They remain at large and are believed to be heavily armed.

Previous: Je Suis Charlie
Gunmen Attack French Satirical Newspaper