Simple Chaos Testing scenario for Kubernetes pods using Chaos Mesch

Question

I'm experimenting with Chaos Mesh to implement the following scenario:

• during 3 minutes kill N pods from specific namespace every 20 seconds
• the overall number of pods to kill is 20% of all pods in the namespace

I started from the simplest PodChaos kind:

apiVersion: chaos-mesh.org/v1alpha1
kind: PodChaos
metadata:
  name: kill-pods-5percent
  namespace: chaos-mesh
spec:
  selector:
    namespaces:
      - services
  action: pod-kill
  mode: fixed-percent
  duration: "3m"
  value: "20"

But CRD object above kills 20% of pods at the very beginning and ignores "duration" property, is it even possible to implement the scenario above with Chaos Mesh? Also would be appreciated for free of charge alternative of Chaos Mesh that could run the scenario. Thanks.