Shots were fired at the offices of a left-wing French newspaper and outside the headquarters of a major bank in Paris on Monday and police said the same gunman appeared to have carried out both attacks.
There was no indication of his motive.
The assailant opened fire at the central Paris office of left-wing daily newspaper Liberation, seriously injuring a photographer's assistant shortly before fleeing, police and staff at the newspaper said.
About 90 minutes later, a man opened fire on the street outside the suburban headquarters of Societe Generale, wounding no one, police and a spokeswoman for the bank said.
Shortly afterwards, a gunman hijacked a car nearby and forced the driver to drop him on the Champs-Elysees Avenue in central Paris, the driver told police. It was not clear if that incident was related to the two shootings.
A police source said the description of the gunman, armed with a hunting rifle or similar weapon, was similar and the cartridges found after both attacks corresponded.
Liberation managing editor Fabrice Rousselot said witnesses described the attacker as a short-haired man in his 40s.
The wounded person was hit in the chest, a police official said, adding that the motive of the attacker was unclear.
"He walked in, fired twice and left," Rousselot told reporters.
Deputy editor-in-chief Fabrice Tassel said in a tweet that the young male victim was fighting for his life in hospital.
"As long as this person is still on the loose and we do not know the motives, this represents a threat," Interior Minister Manuel Valls told reporters outside Liberation's offices after visiting the scene. "We must move fast."
Police deployed outside the offices of other media outlets in the French capital.
The mid-morning incidents came days after an armed intruder entered the offices of the BFM television channel, threatening journalists before disappearing. Rousselot said it was not clear whether those incidents were linked.
Liberation's offices near the Place de la Republique in east-central Paris were cordoned off as forensics experts investigated.