At least 12 people were killed during a shooting at the headquarters of the satirical Charlie Hebdo weekly in Paris, police say.
In a televised briefing, Paris Prosecutor François Molins said "at least two" gunmen entered the offices of the magazine at about 11:30 a.m. on Wednesday, Paris time.
NPR's Eleanor Beardsley reports that the men first shot and killed a police officer stationed at the magazine, then walked up to the second floor newsroom and opened fire.
Four of the magazine's founding cartoonists were killed in the attack. Eleven other people were injured, four of whom are in critical condition.
One video shown on French television shows two masked men leaving the building and then trading fire with another police officer. The officer is injured and one of the men stands above him and kills him at point-blank range. Eleanor says during the exchange, one of the men shouts, "We have avenged the Prophet Muhammad."
Authorities have not yet determined a motive and no organization has taken responsibility.
Of the 12 killed, two were police officers and eight were journalists, said Molins.
The gunmen then got into a black vehicle to escape. They went to a Paris suburb where they abandoned their car and jumped into another.
A massive manhunt is now underway in the Paris area, with some school trips cancelled and some metros closed.