Salt Lake County prosecutors declined to file charges against the police officer who was escorting a man down a set of stairs when that man fell over the railing and later died.

District Attorney Sim Gill outlined his reasoning in a letter sent Tuesday to Salt Lake City Police Chief Mike Brown and Salt Lake County Sheriff Rosie Rivera, saying evidence shows no one contributed to Robert Martinez’s death but himself.

Martinez, 38, died about two weeks after he fell headfirst off a set of stairs during his arrest on April 7. Police were called to his home that night at 204 E. Browning Ave. to investigate a report of domestic violence.

He allegedly had been holding his girlfriend in the house against her will.

When police arrived, Martinez told officers his leg was hurt because he’d been hit by a car in 2017. Medics checked him out and asked him, among other questions, if he felt suicidal or like he would hurt anyone else, according to the letter. He said no to both.

(Photo courtesy Salt Lake County Sheriff's Office) Robert James Martinez, seen here in a booking photo at the Salt Lake County jail in 2017, died April 20, 2019, from injuries suffered in a fall from a staircase while being arrested in connection to a domestic-violence incident on April 7, 2019, in Salt Lake City.

So, Officer Echols, whose first name wasn’t released, walked with Martinez down the stairs, telling Martinez, “We’re going to take it slow, all right?”

Video shows, according to Gill, that when Martinez descends to the fourth or fifth step from the top, he appears to slip and fall over the railing. A witness told investigators the same thing.

Echols declined to interview with prosecutors, but in the incident report from that night, he wrote that he thought that Martinez just needed to take a break when he stopped walking.

“I was mistaken. Martinez jumped over the railing and purposely went headfirst into the ground from about 10 feet high,” he said. "I was unable to stop him from failing even though I tried to hold on. Martinez appeared to be close to 300 pounds close to double my own weight.”

Gill said after reviewing the evidence, it’s unclear whether Martinez fell accidentally or purposely. However, he said, that doesn’t matter.

He wrote his review focused on whether Echols pushed or forced Martinez to fall — and investigators found no proof of that.