Sculptor Olbram Zoubek, an artist known for taking a death mask of Jan Palach, student who burned himself to death to protest the 1968 Soviet-led invasion of Czechoslovakia, has died at age 91.

The Culture Ministry says Zoubek died Thursday in Prague, citing his family.

Jan Palach set himself ablaze in Prague on Jan. 16, 1969, five months after the Warsaw Pact countries crushed the liberal reforms known as the Prague Spring. He died three days later.

Zoubek also made a gravestone for Palach, which was removed by the hard-line Communist regime. Zoubek was also persecuted by the authorities.

His memorial plaque for Palach was unveiled in Prague after the 1989 anti-Communist Velvet Revolution.

Zoubek’s most visible work is his Memorial to the Victims of Communism in Prague.