ORLANDO, Fla. -- A man accused of shooting at George Zimmerman last month now faces an attempted murder charge.

A prosecutor on Thursday upgraded the charges against Matthew Apperson to attempted second-degree murder. Apperson earlier had been charged with aggravated assault and battery for firing a gun into Zimmerman's car during a traffic run-in May 11.

A lawyer for Zimmerman, Don West, has said that Zimmerman was not struck by a bullet but was sprayed with glass from his vehicle's windshield and other debris.

State Attorney Phil Archer said in a statement that people ought to be able to travel the streets without fear. Apperson's attorney, Michael LaFay, said he couldn't comment since he hadn't yet received a copy of the new charge.

Apperson and Zimmerman were apparently in an on-going feud. Last September, Apperson said Zimmerman threatened to kill him, asking "Do you know who I am?," during a confrontation in their vehicles.

Apperson decided not to pursue charges, and police officers were unable to move forward without a car tag identified or witnesses.

After last month's incident, witness Ken Cornell told 48 Hours Crimesider that he dialed 911 and put Apperson on the phone with dispatchers after Apperson told him, "Please call 911, I just shot George Zimmerman." Apperson told police it was his third dispute with Zimmerman, Cornell said.

"He said the cops know who I am, this is an ongoing dispute," Cornell said.

Prosecutors contend Apperson had a fixation on Zimmerman, and a Lake Mary police report alleges that Apperson has mental health issues. Apperson has maintained he fired because Zimmerman pointed a gun at him as they were driving.

A jury acquitted Zimmerman in the shooting death of Trayvon Martin two years ago. The case sparked protests and a national debate about race relations.