A Czech student who gunned down 14 people at a Prague university appears to have gone on two macabre trial runs before Thursday’s deadly attacks.

The killer, who has been named as 24-year-old David Kozak, also injured 25 more people at Prague’s Charles University.

It is the deadliest attack in modern Czech history, and authorities have warned the toll may rise further.

In the hours after the killings – which left students perched on roof-high ledges and barricaded in classrooms as they tried to evade the shooter – it appeared Kozak had shot dead his father earlier in the day.

Because of evidence found in his house after Thursday’s shooting, he is also suspected in the killings of another man and his two-month-old daughter. They were found last week shot dead in woods in a village outside Prague, Police President Martin Vondrasek said.

The Czech government has declared a day of mourning for December 23 to remember the victims, decided at a special cabinet meeting with Prime Minister Petr Fiala and President Petr Pavel.

“I would express my great sadness along with helpless anger at the unnecessary loss of so many young lives,” Pavel said.

“I would like to express my sincere condolences to all relatives of the victims, to all who were at this tragic incident, the most tragic in the history of the Czech Republic.”

Police – who discovered a large arsenal of weapons at the downtown university building where the shooting happened on Thursday afternoon – were tipped off earlier in the day that Kozak was likely heading to Prague from his town in the Kladno region outside the capital, with intentions of taking his own life.

Shortly after that, Kozak’s father was found dead.

Police evacuated an arts faculty building where Kozak was due to attend a lecture. They were then called to the faculty’s larger main building, arriving within minutes after reports of the shooting, Vondrasek said.

Police had “unconfirmed information from an account on a social network that he was supposedly inspired by one terrorist attack in Russia in the autumn of this year”, Vondrasek said, adding the shooter was a legal holder of several firearms.

“It was a premeditated, horrific act that started in the Kladno region and unfortunately ended here,” he said.

The Czech republic has declared a national day of mourning after the deaths. Photo: Getty

Kozak body was later found dead on the university campus. His death is being considered a suicide but authorities are also investigating whether he may have been killed by police who returned fire.

Police said he was a high-achieving student with no prior criminal record and he acted alone.

Interior Minister Vit Rakusan said the shooting had no connection to international terrorism.

As Thursday’s terrifying attack unfolded, authorities sealed off the square and area adjacent to the faculty building, in a busy historical district across the river from Prague Castle on a popular street leading to Old Town Square.

Media images showed students fleeing the building with their hands in the air. Others were perched on a ledge near the roof trying to hide from the attacker, while more barricaded classrooms with desks and chairs.

“Currently stuck inside my classroom in Prague,” Jakob Weizman, a student at Charles University, wrote on X (formerly Twitter).

“Locked the door before the shooter tried to open it.”

University staff were warned of the shooting in an email.

“Stay put, don’t go anywhere, if you’re in the offices, lock them and place furniture in front of the door, turn off the lights,” it said.

Prague mayor Bohuslav Svoboda told local TV that Czechs had always thought mass shootings were not an issue for them.

“Now it turns out that, unfortunately, our world is also changing and the problem of the individual shooter is emerging here as well,” he said.

The White House condemned the shooting and said the US was ready to offer assistance.

Leaders across Europe, including France’s Emmanuel Macron, have offered their support.

Witness Ivo Havranek, 43, told Reuters via Zoom that he initially thought the “couple of bangs” he heard might have come from loud tourists or a nearby movie set.

“Then suddenly there were students and teachers running out of the building. I went through the crowd not realising what is actually going on. I wasn’t ready to admit that something like that could happen in Prague,” he said.

Only once he saw police officers with automatic rifles, he knew it was serious, Havranek said.

“They shouted at me to run away.”

After the shooting, people lit candles outside the historic headquarters of Charles University, which dates back to 1348 and is central Europe’s oldest.

Gun crime is relatively rare in the Czech Republic. In December 2019, a 42-year-old gunman killed six people at a hospital waiting room in the eastern Czech city of Ostrava before fleeing and fatally shooting himself, police said.

In 2015, a man fatally shot eight people and then killed himself at a restaurant in Uhersky Brod.

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-with AAP