Police are offering a R100 000 reward for information that will lead to the arrest and conviction of those who murdered a police sergeant in Lavender Hill three months ago.Donovan Prins was killed on June 24 while pursuing suspects who opened fire on him, Lieutenant Colonel Andrè Traut said."He was wounded and admitted to hospital where he later [died]. The suspects fled and are sought by police."A reward of R100 000 is offered for information that will lead to the arrest and conviction of the suspects."The Anti-Gang Unit is investigating the case and urges anyone who has information to contact investigating officer Detective Sergeant Patrick Learner on 021 843 1900 or Crime Stop on 08600 10111 with an anonymous tip-off.Shot in the headMeanwhile, a memorial service will be held on Wednesday for murdered policeman Warrant Officer Hilton Joseph.Joseph and his colleague, Constable Terrence Mostert from Mfuleni police station, were on patrol at about 22:00 last Sunday when someone they confronted in Diepwater, Wesbank, shot them.The 52-year-old policeman was shot in the head and died in hospital.His partner was wounded in the neck and survived.Police Minister Bheki Cele is expected to deliver the keynote address at the memorial service at the Enon Tabernacle Baptist Church.Two people have been charged for Joseph's murder.