The State Attorney's Office filed attempted second-degree murder charges Thursday against the man accused of shooting at George Zimmerman.

Matthew Apperson is accused of firing a shot at Zimmerman as Zimmerman was driving on Lake Mary Boulevard May 11.

Zimmerman told officers he had been driving in Lake Mary when Apperson got behind his truck and yelled, "You remember me, you (expletive)?"

Apperson then said, “You owe me your life. The only reason I didn’t press charges on you is because I wanted to kill you myself.”

Apperson and Zimmerman had an altercation in September, but Apperson declined to press charges.

Zimmerman said he called Apperson a clown, and Apperson fired a gun at his car a short time later. The bullet flew close to Zimmerman’s head, shattering a window and sending shards of glass all over him.

Police said Zimmerman flagged down an officer to report the shooting, and while that was happening Apperson called 911.

According to the police report, two handguns -- a .40-caliber and a .357 revolver -- were recovered from Apperson's vehicle.

An expended .357 shell was found in the vehicle.

Police also recovered a gun from Zimmerman, who suffered minor injuries in the incident.

Apperson was charged with aggravated assault in the incident. He was ordered by a judge to wear a monitor that alerts Zimmerman when he is nearby.

Along with the attempted second-degree murder charges, Apperson is also charged with shooting into an occupied vehicle and with aggravated assault with a firearm.

"It's not unusual that when a State Attorney's Office reviews an arrest affidavit they file more serious charges or additional charges," WFTV legal analyst Bill Sheaffer said. "This homicide charge changes the complexion of the case. It almost doubles the potential prison time that this defendant will face if he's convicted."

Zimmerman's attorney Don West said he believes the upgraded charge is appropriate.

"It not only is a serious charge, but it also has a mandatory minimum penalty associated with it upon conviction because of the firing of the gun. It's a very serious charge. I talked to George about it and he's very happy that the State Attorney's Office decided to file that charge," West said.

George Zimmerman was in the national spotlight when he was charged with second-degree murder in the shooting death of 17-year-old Trayvon Martin in 2012.

Zimmerman was acquitted of the charges in his 2013 trial.

Lake Mary police said they believe Apperson became fixated on Zimmerman after the acquittal.

Apperson's attorney told Channel 9's Tim Barber that the charges don't change the facts of the case and that it won't change their claims of self-defense.