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WESTMINSTER, Colo. — A court document reveals new details about what investigators believe happened leading up to and during a fatal shooting outside a Westminster dental office Thursday afternoon.

The document is an affidavit for a search warrant. FOX31 received the document from the Adams County Combined Court.

According to the affidavit, Jeremy Webster, 23, followed a woman and her three children into a parking lot near West 80th Avenue and Sheridan Boulevard. Westminster police believe it was a case of road rage.

Witnesses told investigators Webster parked his car in the middle of the parking lot behind the woman’s.

Webster then began arguing with the woman. He produced a handgun and shot her multiple times. When she fell to the ground, Webster then shot two of her three boys multiple times. Webster began walking back to his car before shooting one of the boys again. That boy was pronounced dead at the hospital, according to the document.

The third boy ran away and was not shot.

The affidavit said that after shooting the woman and the two boys, Webster made eye contact with a man who was sitting in his truck with his young daughter. Webster walked toward the truck and shot it multiple times, hitting the man in the arms. That victim then put his truck into reverse and sped out of the parking lot. He is expected to survive. His daughter was not hurt.

After shooting the four people, the document alleges Webster fled the scene in his Toyota Corolla, in which he was later found driving on Interstate 25 near Castle Rock. He was taken into custody.

The road rage incident started near Sheridan Boulevard and Turnpike Drive. The boy who was uninjured said his mother took a picture of Webster’s license plate before they got out of the car, according to the affidavit.

Using this photo, investigators were able to identify Webster as the suspect. When shown a photo of Webster, the man who was shot in his truck identified Webster as the man who shot him.

Once apprehended, Webster admitted to police he shot the woman, the children and the man in the truck. He said he has mental health issues and began taking a new prescription Thursday. He said he used his Glock 19 handgun to shoot the victims.

“All of the victims in this case suffered serious gunshot wounds to different parts of their bodies,” the affidavit said. The three people who were shot but survived the shooting — the mother, one of her sons and the man in the truck — are all in serious condition and undergoing surgeries.

The document lists a Colorado Springs address as Webster’s residence.

Webster was booked into the Adams County jail early Friday morning and is being held for investigation of first-degree murder after deliberation with intent, first-degree murder extreme indifference, first-degree assault and criminal attempt to commit a Class 1 felony.

The victims have no relationship with Webster, police said.