Ferguson’s top cop should resign, the best apology from him will be not words but the arrest and prosecution of the police officer who killed their son, the parents of Michael Brown said as tensions in the St. Louis suburb escalated again this week.

The parents of Michael Brown said they were unmoved by Ferguson Police Chief Tom Jackson’s apology which he offered earlier this week, more than a month after their 18-year-old son was killed by a white police officer.

“An apology would be when Darren Wilson has handcuffs, processed and charged with murder,” Michael Brown Sr. told the AP, while Brown’s mother, Lesley McSpadden, said Chief Tom Jackson should be fired.

The killing by Officer Darren Wilson of an unarmed African-American teen on August 9, sparked weeks of unrest in the predominantly black community of Missouri, while the highly militarized response to protests and demonstrations near the site of the shooting exacerbated tensions and galvanized the local population to call attention to racial grievances.

“There’s going to continue to be unrest until they do what should be done,” McSpadden said, even after Chief Jackson issued an apology on Thursday. “I don’t want words, I want action,” she added.

At the same time, Brown's parents voiced outraged that Ferguson police officers are wearing bracelets in support of the officer who shot the teenager, reading “I am Darren Wilson”. The Justice Department already asked the local the police not to wear such bracelets while on duty.

On the ground in Ferguson, tensions continued to mount following police chief’s apology, which he says was from the heart. A scuffle broke out after Jackson decided to participate in a march for the slain teen and appeared outside police headquarters in civilian clothes to assure protesters calling for his resignation that there would be reforms following Brown’s death. At least 4 people were arrested on Thursday.

Brown's parents are on a crusade to change the monitoring of the US law enforcement system, as they seek the Justice Department to take over the investigation into their son's shooting. They are advocating Congress to pass a bill making it mandatory for police officers to wear cameras on duty as they engage the public.