Ferguson protesters
Protesters march to show their solidarity with the family of black teenager Michael Brown who was shot by a police officer and died in August in Ferguson, Missouri.Reuters

A plot aimed at killing St. Louis County Prosecuting Attorney Robert McCulloch and Ferguson Police Chief Tom Jackson has come to light following the arrest of two men on weapon charges last week.

McCulloch had earlier this week announced the jury's decision not to indict Ferguson shooting officer Darren Wilson, which had led to massive rioting in St Louis county and across the United States. 

Brandon Orlando Baldwin and Olajuwon Ali Davis were arrested on federal weapons charges three days before the final verdict on the Ferguson shooting was out.

It later emerged that the two men had allegedly planned to bomb the iconic Gateway Arch, and to kill McCulloch as well as Ferguson Police Chief Tom Jackson, St Louis Post dispatch reported.

The two men have been charged with abetting the making of a false written statement made in connection with a firearms purchase, after Baldwin had allegedly attempted to buy two Hi-Point .45-caliber pistols for someone else but claiming they were for him.

One of the plans included planting a bomb inside the observation deck at the top of the Arch, a 630-foot tall monument in St. Louis, as per the report.

While their ability to carry out the attack is being doubted, they had reportedly bought what they believed was a pipe bomb in an undercover operation.

It is also unclear how the duo planned to kill McCulloch and Jackson.

Davis had reportedly attended a New Black Panther rally in Ferguson last month, wherein he had said, "This is not the first Mike Brown, and it won't be the last, if we do not unite, Divided, we lose brothers and sisters. If you do not unite, put aside your difference and unite, you can expect no changes in the future. We must change our minds, our systems and ourselves".

The revelations add more tense drama to Ferguson, which has already been on the boil since the jury's decision to let Wilson, who shot dead black teen Michael Brown, to walk without charges.