Traumatic play; re-enacting parts of the trauma in their play (drawings, acting out). Regressive behavior (thumb sucking, bed-wetting).
[anxietybc.com]
They may also start ‘acting out’ and develop disruptive and destructive behaviours.
[sane.org]
[…] who witness the death or assault of a parent will later suffer PTSD Youth with PTSD may experience other problems as well, including depression, other anxiety problems, or acting-out
[anxietybc.com]