Last week, the Wizards and Arenas acknowledged that Arenas had stored unloaded firearms in a container in his locker, and the NBA said it was looking into the situation.
It was during that investigation that a confrontation between Arenas and Crittenton was revealed, according to a Yahoo! Sports report.
The dispute stemmed from an unspecified disagreement, sources told Yahoo! Sports.
Citing an anonymous source, the Post reported in Friday's edition, however, that the standoff was sparked when Crittenton became angry at Arenas for refusing to make good on a gambling debt.
That prompted Arenas to draw on Crittenton, who then also grabbed for a gun, league security sources told the Post.
Asked by the newspaper about the confrontation, Arenas denied pulling a gun on Crittenton.
"This is unprecedented in the history of sports," Billy Hunter, executive director of the NBA players' association, told the Post. "I've never heard of players pulling guns on each other in a locker room."
The Wizards issued a statement Dec. 24 that Arenas had stored unloaded firearms in a container in his locker at the arena and that the NBA was looking into the situation.
On Tuesday, Washington, D.C. police said they were investigating a report that weapons were found inside a locker room at the Verizon Center.
Now, the federal government is also involved. Ben Friedman, a spokesman for the US Attorney's Office in DC, told the Post "we're working with the Metropolitan Police Department on the investigation."