McALLEN - It can be one of the toughest snap decisions that a police officer has to face.

When and how to use force to subdue a threatening suspect can be a tricky business for authorities. Each situation is unique.

"Sometimes it happens so quick, you just reset to your training," said Hidalgo County Sheriff Lupe Treviño, who said he has had to fire upon at hostile suspects at times during his 35-year law enforcement career. "Regular people don't have to follow anything - it's just fight or flight. For us, it's different."

Two incidents this month have shown the difference between how lethal and non-lethal force can subdue hostile suspects.

Monday night, a Harlingen police officer fatally shot 41-year-old Mexican national Diego Rivas Soto, who was reportedly trying to set a fire beneath a U.S. Expressway 77 overpass.

Flanked by two fellow officers and carrying a non-lethal Taser on his body, the officer fired one shotgun shell into the man's upper torso. Rivas had reportedly charged the police with a knife in hand.

Four days earlier, Port Isabel police faced a standoff with a hostile suspect during the early morning hours of New Year's Day.

Jesus Manuel Treviño, 48, had tried to flee authorities before he ended the chase at a house and ran inside.

Treviño eventually came out of the building, waving a handgun toward police. A Laguna Vista officer at the scene fired his Taser at the man causing him to fall to the ground.

"That Taser definitely saved the man's life," Laguna Vista police Chief Robert McGinnis said last week. "And maybe innocent lives, as well."

Each department's policy on use of force against a suspect varies slightly, said McAllen police Chief Victor Rodriguez. But officers are held liable under the same laws as the public.

"We're subject to the law that applies to everybody," Rodriguez said. "It doesn't matter if you're a police officer or a citizen. A person can use force."

Use of force typically escalates when verbal commands have failed an officer, Treviño said. From there, police are taught to progress to hands-on combat, a non-lethal weapon or their gun.

Still, some situations escalate too quickly to exercise every method before using lethal force.

"Sometimes it's verbal to lethal," the sheriff said. "It all depends on the circumstances."

Harlingen police have not released the name of the officer who fired on Rivas or said why he chose his shotgun instead of his Taser during the deadly Monday night incident.

The man is currently on leave from his duties, while the Texas Rangers and Cameron County District Attorney's office continue to investigate. The evidence is expected to be turned over to a grand jury for consideration.

But most law enforcement-led investigations into the use of deadly force reveal the officer did no harm - even if that may not be the truth, said George Vincentnathan, head of the University of Texas-Pan American's Criminal Justice Department.

"There (can be a sentiment) that whenever a police officer does something bad and irresponsible, you should cover up what the brother has done," he said. "If he has done something extra or excessive, that will usually be covered up."

The Valley Morning Star and Island Breeze contributed to this report.

Jared Taylor covers law enforcement and general assignments for The Monitor. You can reach him at (956) 683-4439.