Arroyo, who had parked and lay in wait nearby the courthouse, approached his ex-wife and son on the steps outside the Smith County Courthouse and fired on them with a semi-automatic MAK-90 rifle, a semi-automatic rifle styled after the AK-47 rifle. Maribel Estrada was hit in the head and killed instantly, and Arroyo Jr was hit in the leg and wounded. Both fell to the ground at the front courthouse steps.
Nearby law enforcement and law enforcement officers already present at the courthouse responded to the initial shots and began exchanging fire with Arroyo. At this point, the law enforcement officers were only armed with pistols, and Arroyo was able to wound several and force them to retreat.
A local resident, Mark Allen Wilson, was in his downtown loft when he heard the shooting begin. He looked out his window and saw Arroyo at the courthouse steps engaged in a shootout with law enforcement. Wilson, who held a Texas concealed handgun permit immediately armed himself with his Colt .45 caliber pistol, and left his residence to intervene in the gun battle. Because Arroyo was already engaged in a heated gun battle with sheriff's deputies and Tyler police officers, he did not see Wilson approach from behind.
As Wilson approached Arroyo from behind, Arroyo was taking aim at his son who he had already shot in the leg and wounded. Acting to defend the life of Arroyo's son, Wilson fired a round from approximately 50 feet which struck Arroyo in the back causing him to stumble and taking his attention away from his son. A witness who saw Wilson's round strike Arroyo reported seeing "white puffs of powder-like substance" come from Arroyo's clothing. This is believed to be the first time Arroyo was hit or injured during his attack on the courthouse.
Wilson was forced to take cover behind Arroyo's truck in a prone position and exchanged fire with Arroyo. As Arroyo began to approach Wilson's position, he stood up from behind cover and fired again hitting Arroyo. Unknown to Wilson, Arroyo was wearing a bulletproof vest rendering Wilson's shots largely ineffective. Arroyo eventually fired a shot that struck Wilson who faltered and fell from the view of witnesses face down behind Arroyo's truck. Arroyo then fired three more shots at Wilson killing him.