London’s police department has reopened its investigation into the unsolved 1987 murder of the Palestinian political cartoonist Naji al-Ali, whose work criticizing Israeli and Arab politics has become iconic in the Middle East in the decades since he was shot outside a newspaper office.

The Metrolitan Police Service appealed for the public’s help on Tuesday, the 30th anniversary of the cartoonist’s shooting death outside a newspaper office in London. The police also released descriptions for two suspects in the case, including an artist’s rendering of what they believe the gunman would look like today.

“We have previously reviewed this case and followed a number of lines of enquiry which have not resulted in us identifying these two men,” Cmdr. Dean Haydon, head of the Metropolitan Police Counter Terrorism Command, said in a statement. “However, a lot can change in 30 years — allegiances shift and people who were not willing to speak at the time of the murder may now be prepared to come forward with crucial information.”