Polish Foreign Minister Witold Waszczykowski has offered his condolences over a gun massacre targeting a gay nightclub in Orlando, Florida, over the weekend.

“We are deeply moved and struck with grief by the shocking news coming from Orlando,” Waszczykowski wrote in a message sent to US Secretary of State John Kerry on Monday.

The deadliest shooting in US history left 50 people dead and 53 injured, after 29-year-old Omar Mateen opened fire inside the Pulse, a popular gay nightclub in Orlando, Florida, on Saturday night.

“On behalf of the Polish Ministry of Foreign Affairs and myself, I wish to express our deepest condolences. Our thoughts go to the families and friends of the victims as well as to all people affected by this tragedy,” reads the foreign minister’s statement.

Waszczykowski expressed hope that the circumstances of the tragic event would be “thoroughly examined and that those responsible will be promptly brought to justice.”

Omar Mateen, a US citizen of Afghan origin, is believed to have been acting alone. Preliminary findings indicate that the gunman was inspired by the Islamic State (IS), but no evidence has surfaced as yet to prove he had links to the fundamentalist militant group.