UPDATE: France was on high alert after a gunman ambushed three Parisian police officers on the Champs-Elysees on Thursday, killing one and wounding two others in what the country's president called a terrorist attack.
The gunman — who ISIS claimed as one of their own — was then fatally shot while trying to to flee on foot down the famed boulevard, police said.
"We are greatly determined to fight terrorism here and every place where our forces are engaged," French President Francois Hollande said in the aftermath. "My thoughts are with the family of the police officer killed and those close to the wounded."
Hollande did not identify the slain suspect. But he was known to French authorities and armed with an AK-47 rifle, two U.S. law enforcement officials briefed on the attack told NBC News.
A short time later, ISIS released a statement through the Amaq Media agency in which it claimed credit for the carnage and identified the shooter as "one of the Islamic State fighters."
It also suggested the gunman was from Belgium, which sits on France's northern border and which has also been hit by other ISIS terrorist attacks.
French authorities were searching the gunman's home in the Paris suburb of Chelles and looking for possible accomplices.
Earlier, Interior Ministry spokesman Pierre-Henry Brandet gave the first official account of the mayhem, saying that the "police officers were deliberately targeted."
The shooter pulled up beside a parked police car near the Franklin Roosevelt Metro station and opened fire around 9 p.m. local time (3 p.m. ET), he said. The attacker was shot dead by police, he said.
In the chaos, a female passersby was wounded, Brandet said. Officials later said a tourist was injured by fragments from the shooting. One of the wounded officers was described as being seriously hurt.
Witness Foday Fofamah told NBC News the shooter was driving an Audi and he saw the man jump out and open fire on the officers.
In Washington, President Donald Trump said it "looks like another terrorist attack" before Hollande confirmed that was the case.
"What can you say?" Trump said. "It just never ends."
Meanwhile, as France's elite anti-terrorism took control of the crime scene and searched the shooter's car for possible explosives dozens of police officers kept the curious away.
"The area is dangerous because of shooting," a police officer yelled at reporters in English. "You have to stay back."
The deadly shooting happened as France is in the midst of a hard-fought presidential election.
Marine Le Pen, one of the candidates and leader of France's far-right National Front, tweeted her support of the officers.
"Emotion and solidarity for our security forces, again being targeted," she wrote.
Le Pen's rival, Francois Fillon, also tweeted his support. "Tribute to the security forces who give their lives to protect ours," he wrote.
Candidate Emmanuel Macron chimed-in as well. "Tonight I would like to express my solidarity with respect to all of our security forces," he tweeted.
Paris Mayor Anne Hidalgo said the city would be unbowed by what appears to be the latest in a series of terrorist attacks targeting the country.
"Tonight, a terrorist blinded by hatred and death, shattered the life of a policeman and wounded two of his colleagues on the Avenue des Champs-Élysées," Hidalgo said in a statement.
"I know that the determination of the Parisians to defend their way of life and their values is total. We will not yield, we will not stand back, we will remain united in the face of this odious and deceitful threat that weighs on all of the world's metropolises," Hidalgo said.
ORIGINAL STORY: One police officer has been killed in a shooting in Paris on Thursday and the attacker has been "taken down," according to CNN affiliate BFMTV.
BFMTV also reports another police officer was seriously injured and an unidentified man was hit by "cross-fire" in the the Champs-Elysées area. BFMTV has not specified if the unidentified man was the attacker or a bystander.
BFMTV reported earlier that two policemen were seriously injured.
The Champs-Elysées has been closed and authorities are telling people to avoid the area. Video showed the normally busy avenue, one of the most famous streets in the world, empty of residents and tourists but teeming with security officers at 9:30 p.m.
French police tweeted, "Police intervention underway in the area of the #ChampsElysees avoid the sector and follow the instructions of the police forces."
CNN's Paris bureau is witnessing a large police operation in the area.
The shooting comes three days before French general elections and Paris was already in a state of heightened alert.
Developing story - more to come