At least one person is reported to be dead in Moscow after a shooter opened fire Thursday evening at the highly secure headquarters of Russia’s Federal Security Service, or FSB, according to several Russian news outlets.

Heavy gunfire erupted outside the Russian spy agency in Lubyanka Square, where social-media footage shows several police officers running near the building with assault rifles. A Federal Security Service security officer was fatally shot during the attack, according to the agency, and the gunman involved was “neutralized.”

According to Reuters, the shooting incident may have been planned to coincide Putin’s commemorative speech for Russia’s day of the security services.

“An unknown person opened fire near building #12 on the Bolshaya Lubyanka street,” the security agency said in a statement, according to the Interfax news agency. “Some people were injured.”

The Health Ministry said that five other people were wounded in the shooting, including two Federal Security Service personnel, the Interfax news agency reported.

The building is in a neighborhood that is known to be in one of the most highly secured parts of Moscow.

One witness told Reuters she had heard shots fired in the same area and sirens, gunfire, and screams were heard by several people. In addition to the FSB building, Lubyanka Square is also a busy shopping destination popular with tourists and about a five-minute drive from the Kremlin.

Robert Anchipolovsky, a musician told The Associated Press he was on the way to his concert in Moscow when the shooting began.

“I thought it was fireworks and then I saw how police started to fall on the tarmac and crouch down,” said Anchipolovsky, who filmed the incident from his car.

The attack came on the same day President Vladimir Putin gave his annual televised news conference, in which he hailed Russia’s continued political stability. Putin himself is a former agent of the KGB, the predecessor agency of the FSB. As the gunfire started, he was at a gala at the Kremlin to celebrate “Security Agency Worker’s Day,” a government website reported.

“Today we honor the people who have chosen a very difficult but also very important path for the state and society; those who staunchly defend Russia’s national interests and security, uncover and neutralize internal and external threats, and protect the lives, rights and constitutional freedoms of all Russians,” Putin said in his Security Agency Worker’s Day speech.

At around 7:15 p.m. local time, the news outlet Meduza reported that FSB press officers said a gunman had also been killed, and officials were working to establish his identity. The outlet said its correspondent continued to hear gunfire in the area after that time.

Fifteen minutes later, the “siren” alert, indicating the search for an active shooter, was activated throughout the capital, according to Baza. The agency also activated their “fortress” plan—which puts all buildings in total lockdown.

Russian investigators have opened criminal proceedings into the attempted murder of law-enforcement officers after the incident, Reuters reported.