With the first round of voting scheduled for Sunday, center-right candidate Francois Fillon, far-right candidate Marine Le Pen and leftist candidate Emmanuel Macron announced they suspended their campaigns.
In opinion polls, the three lead the list of presidential candidates in popularity. The three took part in a televised debate Thursday evening when the shooting on Paris' Champs-Elysees occurred.
A single gunman with an automatic rifle opened fire on a police bus on Paris' most prominent street, and was shot by the return fire of security forces as he attempted to escape.
Two other police officers were injured in the incident, Interior Ministry spokesman Pierre-Henry Brandet said.
"On the face of it, the officers were deliberately targeted," Brandet said.
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