How do I activate a lightbar from a parked emergency vehicle?

[nicesbrot 0]

Hey there,

sorry if this question seems pretty dumb but I'm new to the rph develement. 
I'm currently making a lspdfr callout where I need to spawn some policecars to create a crime scene. I couldn't find a possibility to activate the  lightbars from the parked vehicles. Does anyone have an idea how I can turn them on? 

Thanks for your help and have a nice day. :)

[sEbi3 269]

If you want the lightbars with siren:
 

PoliceVehicle.IsSirenOn = true;

 

If you want the lightbars without siren:
 

PoliceVehicle.IsSirenSilent = true;