Cape Town - Five people have been taken in for questioning following the death of a top police officer on Wednesday morning.Warrant Officer Petrus Holz, 50, was stabbed to death on the N2 near the Makhaza turn-off, Hawks spokesperson Brigadier Hangwani Mulaudzi said on Wednesday.He said Holz, who was a member of the commercial crimes unit of the Hawks, had stopped his car to check if "everything was okay" after debris was strewn across the road.Holz started his career in the police on June 30 1992, and joined the Commercial Crime unit in 2007.“This is a bad day for the police, a very bad day,” Mulaudzi said, referring to the policeman who was killed in Vosloorus earlier on Wednesday.Gauteng police have launched a manhunt for a gang of armed robbers who shot and killed a 36-year-old policeman who was on duty at the Vosloorus Crossing Mall at 07:30 on Wednesday.A group of about six suspects fled the scene with two vehicles, a silver Nissan Tiida and white Audi A4. A Nissan Tiida was found abandoned at Vosloorus extension two, police said in a statement. Police are looking at the CCTV footages to identify the killers.Western Cape police spokesperson Colonel Thembinkosi Kinana said the two suspects who robbed and stabbed Holtz around 05:00 were are still at large.The officer was in an unmarked car and in civilian clothing when he was attacked.Acting provincial police commissioner Major General Thembisile Patekile extended condolences to the Holz’s family, friends and colleagues.There has been a spate of robberies and attacks on the highway in the past few months.In May, a part-time DJ was attacked by a gang of robbers near the Duinefontein off-ramp, the Cape Argus reported.In the same month, two would-be robbers got more than they bargained for when they tried to rob an undercover metro police officer on the N2 near Cape Town, News24 reported.The plain-clothed cop had been stationed at the roadside in a bait car in a planned operation on the so-called N2 “hell run” between the Mew Way and R300 off-ramps.One of the alleged robbers, armed with a knife and a toy gun, was arrested after the robbery attempt.Murder condemnedThe Western Cape MEC for Community Safety, Dan Plato, strongly condemned Holtz's murder."I extend my deepest condolences to the family, friends and colleagues of the slain officer on their loss. The death is one that should never have been allowed to occur."He said safety on the N2 remains a major concern, and the recent spate of incidents shows the brazen lengths criminals will go to, as well as their total disregard for life."I call on the people living in communities next to the N2 highway to speak up against the criminals in their midst, to assist the police in their investigation and to ensure that those responsible for these heinous crimes are identified and arrested."He called on the South African National Roads Agency (Sanral) to erect and maintain sufficient fencing along the N2 to prevent access to the highway, and for police to arrest any pedestrian on the highway in terms of the National Road Traffic Act.