The men wanted to acquire two more bombs, the sources said, but could not afford to do it until one suspect’s girlfriend’s Electronic Benefit Transfer card was replenished.

An indictment, with no mention of bombs or killings, was returned in federal court here Nov. 19 and unsealed Friday upon the arrest of Brandon Orlando Baldwin and Olajuwon Ali Davis. Their addresses and Baldwin’s age were not available; Davis is 22.

The arrest came three days before McCulloch revealed that a grand jury would not indict Ferguson police Officer Darren Wilson in the controversial killing of Michael Brown. The announcement triggered looting and multiple arsons in Ferguson.

The charges say that between Nov. 1 and Nov. 13, at the Cabela’s store in Hazelwood, Baldwin claimed to be buying two Hi-Point .45-caliber pistols for himself when they were really for another person. Brandon also is known as Brandon Muhammad, according to court documents, and Davis now goes by the last name Ali, his attorney said. Each faces a charge of aiding and abetting the making of a false written statement made in connection with a firearms purchase.

The sources said additional charges, reflecting the plot, were expected to be filed. They said Davis was considered the leader of the plot, which police documented on hidden video.

The firearm charges and arrests were reported by the Post-Dispatch on Friday night. Some national news outlets reported, with no detail, that there had been a bomb plot.

One of the defendants’ plans, the sources said, included planting a bomb inside the observation deck at the top of the Arch. It was not clear how they could have gotten a bomb past airport-style security screening for rides up.

It also wasn’t clear, the sources said, whether the men intended to use bombs as the means to kill McCulloch and Jackson. Both officials became targets of national criticism and protests after Brown’s killing.