SAN ANTONIO – An affidavit obtained by KENS 5 details how witnesses helped San Antonio police officers zero in on the man they believe killed SAPD Detective Benjamin Marconi.

On Sunday 50-year-old Det. Marconi was shot and killed outside of the Public Safety Building in the 300 block of South Santa Rosa while writing a traffic ticket in his patrol vehicle.

The suspect, 31-year-old Otis Tyrone McKane, was arrested Monday on capital murder charges.

The affidavit states that Marconi was in the process of writing what believes to be a traffic ticket when a black Mitsubishi Galant pulled behind Marconi’s patrol car. A witness stated to police a male, who he later identified as McKane, approached Marconi’s vehicle and fired two shots before running back to his car and fleeing the scene.

The Medical Examiner’s Office found Marconi suffered two gunshot wounds to the head. The first to his face and the second to the back of his head.

A witness was driving on the opposite side of the street and slowed down to observe the scene when he noticed the black Mitsubishi park behind Marconi’s vehicle. According to the affidavit, the witness reported he believed something was about to happen when he noticed the black car.

The witness gave police a detailed statement and positively identified McKane as the shooter after multiple pictures of similar looking men were presented to him.

On Monday, an SAPD officer was responding to an unrelated call in the 1200 block of Lombrano. He noticed a black Mitsubishi Galant with the same distinctive rims that were recorded fleeing the crime scene a day earlier. This vehicle was registered to McKane.

According to the affidavit, around the same time on Monday a worker at a tire rental business reported to police he worked and installed the rims and tires on a black Mitsubishi Galant for McKane weeks ago. He reported McKane paid for the rims and tires in installments. He came into the business often to make the payments.

With the help of multiple witnesses, the affidavit states that McKane is believed to have intentionally and knowingly caused the death of Detective Marconi.