The law enforcement community across North Texas is heartbroken following the loss of one of its own.
Officer A.J. Castaneda died Friday after a driver lost control and slammed into his cruiser.
It was an off-duty officer from another jurisdiction who sprang into action.
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Officer Michael Gresham was with his family, headed out of town, when he noticed something that just didn't sit right with him. He noticed a red car and a police cruiser, but no officer.
"As we were passing and we didn't see the officer anywhere around. That was the first time something clicked like, 'This is not good, there's something not right about this,'" Gresham said.
Gresham pulled over and got out of his car and there was still no sign of the officer he'd expected to see -- but there were pedestrians.
"They were peering over the ledge of the bridge. And I was like, 'No, no please no,'" he said.
They were on the side of President George Bush Turnpike Friday morning.
As he walked closer, he looked over the bridge and his heart sank.
"And I looked over the bridge and that's when I saw Officer Castaneda," Gresham said. "My heart immediately just went to the floor."
A 17-year-old driver lost control and hit Castaneda as he was parked on the shoulder, running radar.
Though off duty, and not in his jurisdiction, Gresham knew exactly what do.
"I jumped in his Tahoe, keyed up, identified myself as Officer Gresham with Arlington PD, ID 2651. You have an officer down," he said.
Castaneda didn't survive. The 38-year-old leaves behind an 11-year-old son with special needs.
Gresham can't help but wonder if things could've been different.
"My heart just breaks for officer Castaneda and his family. Grand Prairie PD. I'm so sorry guys," he said. "I wish I could've gotten there just a couple of minutes sooner."
The Grand Prairie Police Department will host a candlelight vigil Sunday at 8:30 p.m. at police headquarters.