When Ferguson, Mo., police officer Darren Wilson left the scene of the fatal shooting of unarmed teenager Michael Brown, the officer returned to the police station unescorted, washed blood off his hands and placed his recently fired pistol into an evidence bag himself. Those actions, described in grand jury testimony, violated protocols for handling a crime scene and securing evidence, according to experts in policing procedures and Justice Department documents. Wilson’s movements after the shooting were among a number of police actions in the aftermath of Brown’s death that experts said were unusual.