Merkel dared to show her head, too.

(CNN)At least 3.7 million people, including world leaders, marched in anti-terrorism rallies in Paris and elsewhere in France on Sunday, French officials said, calling the massive gathering in the nation's capital the largest in France's history.
The day was emotional and peaceful, a gesture of unity just days after Islamic extremists slaughtered 17 people.

Others carried signs that echoed the now-famous phrase that honored slain journalists at the magazine Charlie Hebdo, "Je suis Charlie."

Zineb El Rhazoui, a journalist at the magazine, talked about the magazine's financial struggles and the difficulty of working under constant threats: "I am very happy for all this help, but for us, it was a heavy price to pay, and it is too much.
"It took 12 deaths for us to finally be a little bit understood after we have been hated and booed by everybody."
For the guards and police officers who lost their lives in last week's attacks in France, there were signs reading "We are all cops."

For Muslims in France who want to convey that the ideology embraced by the Muslim gunmen does not represent the whole of the faith, signs read "We are all Muslims."

End to a bloody week
Sunday brought the end to a traumatic week in France.

Brothers Cherif and Said Kouachi, the Charlie Hebdo gunmen, were killed Friday after one of two violent standoffs. Twelve people were slain at the satirical magazine offices on Wednesday.
In the other standoff, Amedy Coulibaly, suspected in the shooting death of a police officer, was killed by security forces Friday after he shot and killed four hostages during a siege at a kosher market

French law enforcement officers were told to remove their social media presence and carry their weapons at all times, because terror sleeper cells had been activated over the past 24 hours in the country, a French police source who attended a briefing Saturday told CNN terror analyst Samuel Laurent.

Coulibaly had made several phone calls about targeting police officers in France, according to the source.

A video that appears to show Coulibaly pledging allegiance to terror group ISIS leader Abu Bakr al-Baghdadi is being shared on Jihadist websites.

Brian Hale, the spokesman for the U.S. director of national intelligence, told CNN on Sunday that the U.S. intelligence community is "aware of the video and is reviewing it to determine its authenticity."

More threats
Threats against people outside of France, particularly against journalists, persisted Sunday.

The offices of Belgian newspaper Le Soir were evacuated Sunday after members of the newsroom received an anonymous phone call of a bomb threat, the newspaper reported. Police locked down the street where paper operates.

And officials in the New York City Police Department responded to a threat from ISIS after someone re-released a September 2014 message that tells followers to "rise up and kill intelligence officers, police officers, soldiers, and civilians," specifically naming the United States, France, Australia and Canada as targets.

NYPD employees were told to "remain alert and consider tactics at all times while on patrol," especially in light of the attacks in France last week, in an internal memo.

The Federal Bureau of Investigation and the U.S. Department of Homeland Security issued a similar bulletin to law enforcement. Both notices make clear that the threat is consistent with previous threats ISIS and others, including al Qaeda, have made.