People gather for a moment of silence Wednesday in Lyon, France, to pay their respects to the victims of the deadly attack at the Charlie Hebdo offices.
A massive manhunt continued into a second day Thursday as police in France searched for the remaining two at-large suspects in the deadly shooting at Parisian satirical newspaper Charlie Hebdo.
The threat alert remained at its highest level, with hundreds of police and security officers activated to help protect public spaces, transportation hubs, religious centers and media outlets from further attacks. President Francois Hollande said France had thwarted multiple terrorist attacks prior to Wednesday’s incident, in which police believe brothers Said Kouachi, 34, and Cherif Kouachi, 32, along with 18-year-old Hamyd Mourad, stormed the Charlie Hebdo offices in a residential area of Paris, killing at least 12, before escaping in a black car.
Mourad turned himself in late Wednesday, police say, reportedly after seeing his name and likeness distributed through social media. There have been multiple other arrests in connection to the attack.
Police descended on a gas station in the Aisne region to the northeast of Paris following reports the two remaining suspects had robbed it. Helicopters hovered above the site, the AP reports. The pair stole fuel and food and fired shots as they left, according to the BBC.
At least one of the Franco-Algerian Kouachi brothers has a history with extremist activity. Cherif Kouachi was convicted of terrorism charges in 2008 and served 18 months in prison.
Both men should be considered heavily armed and very dangerous, French police said in a bulletin published Thursday.
A policewoman died Thursday in a shooting incident in southern Paris. That shooter also remains at large, and it is unclear whether the incident is connected to the attack on the Charlie Hebdo offices.
[READ: Charlie Hebdo Attack in Paris Professionally Orchestrated, Experts Say]
The possibility of a new attack “is our main concern,” said Hollande, as his country begins three nationwide days of mourning with flags flying at half-staff.
And it also represents the realization of Western fears that Islamic extremists with battlefield training in Syria and Iraq, and bearing European or U.S. passports may return to their home countries to carry out attacks like the shooting at Charlie Hebdo.