(CNN) -- Police in northern Virginia charged Washington Redskins defensive lineman Albert Haynesworth with assault Saturday for punching a fellow motorist last week.

Haynesworth, 29, was free to leave after signing the warrant and is scheduled to appear at the Fairfax County Criminal Court on March 31, the Fairfax County Police Department said.

The charge stems from an allegation by an unnamed driver who said Haynesworth punched him February 2 while they were driving on the Fairfax County Parkway, police said.

The motorist told police the driver of a pickup truck -- whom police later determined to be Haynesworth -- was tailgating him, so he delivered a "nonverbal hand gesture" to the driver, Officer Shelley Broderick said.

The man told police that when the two stopped at a red light, Haynesworth got out of the truck and the two briefly exchanged words before Haynesworth threw a punch, according to Broderick.

The man called police. After making a statement, he drove himself to a hospital for treatment of minor injuries, Broderick said.

Police said officers interviewed Haynesworth on Saturday at the Reston District Police Station before he signed the warrant.

Haynesworth's agent, Chad Speck, said last week it was the other driver who instigated the incident and called the accusation "ridiculous."

In Virginia, simple assault is a misdemeanor punishable by up to 12 months in jail and a $2,500 fine.