A 19-year-old man remains the main suspect in a fatal shooting at a Denver 7-Eleven that witnesses claimed started as a shootout.

The Denver Police Department arrested Fabian Vasquez on suspicion of two counts of first-degree murder and one count of attempted first-degree murder following an alleged exchange of gunfire with a police officer early Monday morning. 

Police also arrested 18-year-old Dominic Gallegos on suspicion of being a previous offender in possession of a handgun. Police said Gallegos’ involvement in the incident is under investigation but that it appears he was involved in the argument that sparked the incident.

Two people were killed during the series of events at the 7-Eleven gas station near East 35th Avenue and Colorado Boulevard — in the Clayton neighborhood — around midnight Monday, according to arrest affidavits.

Officers heard gunfire at the store and approached the scene and confronted an armed individual, later identified as Vasquez, who allegedly fired at police. 

The officers returned fire before Vasquez ran from the building, according to the arrest records. 

Vasquez was found hours later hiding behind a building in the 3300 block of Jackson Street, just a few blocks away from the initial scene. A handgun was also found nearby.

At the store, officers found a 30-year-old man lying dead in the parking lot with multiple gunshot wounds. 

A second victim, a 42-year-old man, was found with a gunshot wound in the doorway of the store. He was taken to a nearby hospital, where he later died.

Witnesses claimed that the incident started as an altercation between two groups.

The brother of one of the victims told police that they had entered the store and the victims started arguing with Gallegos, according to arrest records. 

The witness claimed that Gallegos and his brother both pulled handguns in the parking lot before the brother was shot. He was unsure if the brother returned fire.

He also claimed that a man, who he thought to be Gallegos, walked up and shot his brother multiple times at close range while he was on the ground.

One witness, a paramedic in full uniform, entered the store right before the shooting and ducked down when gunfire began. She then saw the 42-year-old victim drop down inside the front of the store. 

The witness noted that the victim had a handgun. She kicked it away and began performing CPR on the man until transportation arrived.

The partner of the paramedic said he saw a fight ensue outside of the store before hearing a single gunshot. As he tried to move the ambulance, he heard multiple other shots in the parking lot.

Police said security camera footage showed Gallegos arguing with the victim in the parking lot before Vasquez got out of a vehicle and began firing shots at the party. He then walked up and shot one of the victims at close range, according to arrest records.

Officers then arrived and ordered Vasquez to put his hands up before he began firing at them.

The Denver police officer involved in the gunfire exchange has been placed in an off-line assignment pending the outcome of the investigation, as is the protocol.

The Denver District Attorney will determine exact charges for Vasquez and Gallegos.

The Denver Office of the Medical Examiner will identify the victims following investigations.

7-Eleven representatives did not respond to a request for comment by the time of this report.

Vasquez is due in court on Thursday. Gallegos, who has not been charged in Denver, has court dates in Lake County and Weld County in February on separate cases.