AMSTERDAM (Reuters) – A Dutch lawyer in a high-profile case against a group of men charged with a series of drug-related killings was shot dead in Amsterdam on Wednesday morning, police said.

Police said the victim was 44-year-old lawyer Derk Wiersum, a defense lawyer for Nabil Bakkali, a crown witness in the case against 16 men accused of five murders and one attempted murder in the Netherlands between 2015 and 2017.

Police said they were searching for a 16 to 20-year old man, who ran away after the shooting, which took place shortly after 7.30 a.m. local time (0530 GMT).

Bakkali is among those accused in the case, which is likely to go to trial next year, but has since 2017 provided police with over 1,500 pages of statements against the group in return for a lower sentence, preliminary court proceedings have shown.

His brother, who police say had nothing to do with the gang or the murders, was killed at his workplace last year, a week after justice authorities said Bakkali was their crown witness.

The prime suspect in the case is 41-year old Ridouan Taghi, who remains at large. Through his lawyer, Taghi has denied all accusations. Other suspects, 11 of whom are in custody, have remained silent throughout the case so far.

Reporting by Bart Meijer; Editing by Andrew Heavens and Catherine Evans