The postings about the March 23 robbery of International Bank of Commerce at 1545 Eldridge were included in a criminal complaint unsealed this week. The arrests, including two bank employees, were announced Thursday.
Security video shows two armed, masked suspects robbing the bank and fleeing with about $62,000.
A tip directed law officers to a pair of Facebook pages.
Federal investigators say one suspect's Facebook page boasted: "IM RICH."
Another said: "WIPE MY TEETH WITH HUNDREDS."
Nobody was injured in the robbery.