AUGUSTA — Four people were arrested Sunday after an incident in which two of them fired guns during a dispute outside Wal-Mart, police said.

Police armed with rifles surrounded the woods south of the University of Maine at Augusta in search of a possible fifth suspect.

In a media briefing Sunday evening, Augusta police Sgt. Christian Behr said shooting broke out between people in two vehicles at the Wal-Mart parking lot. After the shooting, one suspect emerged from one car and confronted people in the other car. The altercation was interrupted by two armed civilians.

Behr said apparently the people in the vehicles knew each other and later Sunday said that heroin was involved.

Charged in connection with the incident were:

• Kwiesha “Reggie” McBride of Harlem, New York, charged with reckless conduct with a firearm, Class C, and aggravated trafficking in drugs, Class B. His bail set at $50,000.

• Frankie Dejesus of Rochester, New York, charged with reckless conduct with a firearm, Class C, and aggravated assault, Class B. His bail set at $25,000.

• Diana Davis of Rochester, New York, charged with aggravated assault, Class B. Her bail Set at $5,000.

• Samantha Tupper, of Augusta, charged with probation violation and furnishing drugs, Class B. She was held with out bail.

The department confirmed via Twitter at 8:15 p.m. a shooting incident had taken place. Shortly afterward, Augusta police posted a description of the incident on the department’s Facebook page:

“At approximately 5:30 p.m., there was an altercation outside of Wal-Mart between several individuals. The altercation developed into two of the people involved firing guns. NO ONE was injured during the altercation or exchange of gun fire. At this time four people are in custody to include the two who were firing the guns. Information obtained at this time is that there is one female who was involved that fled the area. (Dog units) are being used to try and locate her. All of those involved in the incident were acquainted with each other in some way.”

The mention of no injuries notwithstanding, officers at the shooting scene pointed to a blood trail on the ground and to what they said were shell casings. Crime scene tape blocked off an area around a silver Volkswagen Passat with its doors open.

Officers from the Augusta Police Department, the Maine State Police and the Kennebec County Sheriff’s Office participated in the search for the missing woman Sunday along Civic Center Drive and into the woods east of there.

In addition to the state police and Kennoebec County Sheriff’s Office, the Hallowell, Winthrop, and Capitol police departments also assisted.