DALLAS (CBSDFW.COM) – The former Mesquite Police officer facing prison time for shooting an unarmed man, broke down in tears on the witness stand Monday during his aggravated assault trial.

Prosecutors say Derick Wiley shot an innocent man.

Derick Wiley on the stand in his aggravated assault trial (CBS11)

On the stand, Wiley said, “It was in a split second, and I told myself, Derick do not die out here.”

An emotional Wiley said he feared for his own life when he shot Lyndo Jones, who was in his own truck in a vacant parking lot smoking marijuana.

Lyndo Jones testifies in Derick Wiley’s aggravated assault trial (CBS11)

Wiley said he thought Jones was armed.

“I would not have shot that dude if I didn’t think he had a weapon or was going to hurt me, but I didn’t know what he was doing,” said Wiley. “My intention was to handcuff him. Why? Because I thought he had a weapon.”

Jones’ attorneys said they don’t buy it.

“I think those tears were coached, just as his testimony on the stand,” said Justin Moore, one of Jones’ attorneys.

The state argues you can’t shoot someone because you think they may have a weapon.