A deranged man allegedly set fire to a Pennsylvania home after a woman living there rejected his romantic advances — killing an accomplished Army vet and seriously wounding two others, according to authorities.

Robert Zimmerman, 40, was arrested after allegedly starting a deadly inferno that tore through a home in Lewiston around 11:55 p.m. on Wednesday, according to the Lewiston Police Department.

Multiple witnesses reported Zimmerman was at the home — which was rented out to several subletters — to profess his love for a woman living in the attic, police said.

“It was reported that Zimmerman became upset when he was rejected by the female, and he began setting several items on fire on the first floor of the residence,” cops wrote in a statement.

Emergency responders rushed to the scene and found several horrified residents who told police the fire was an arson and that more people were trapped inside.

Brandy Phillippe, 44, tried to escape but was ultimately trapped in the residence. She was later found dead, according to the Mifflin County Coroner’s Office.

A man in the home jumped from the second floor to escape the growing fire and suffered significant facial injuries. He was flown to a trauma center for internal burns in his throat, police added.

Firefighters also rushed to help a woman hanging out a second-floor window, but she refused to jump despite the thick smoke and flames shooting from the property.

Police believe she passed out from the smoke and fell onto a concrete sidewalk below, sustaining “significant injuries,” and was flown to a trauma center.

Zimmerman was allegedly spotted admitting to starting the deadly inferno and seen standing in a nearby alley to watch as the residence erupted in flames. Surveillance images later corroborated witnesses’ statements, police said.

The firebug was located and taken into custody on an outstanding warrant, with cops noting he “smelled like “ash and smoke.”

After Zimmerman was arrested, he declared he had ingested fentanyl and began showing signs of an opioid overdose.

He was taken to a hospital for treatment and later brought back to police custody for questioning — where he made “several incriminating statements,” according to cops.

When police told Zimmerman someone died in the fire, he displayed a “strong emotional response,” police wrote in a statement.

It isn’t immediately clear whether Phillippe was the woman who initially rejected his advances, but the coroner’s office announced they are investigating her death as a homicide.

Phillippe was a “woman of many talents” and a “proud” US Army veteran who specialized in Patriot missiles during her service, according to her obituary.

She also had a background in culinary arts and attended flight attendant school. Later in her life, she worked as a professional truck driver.

“She had a passion for cats and loved many over the years,” Phillippe’s obituary said.

Zimmerman was taken into custody and booked into the Mifflin County Correctional Facility on an outstanding warrant.

Charges are expected to be filed against him in connection with Phillippe’s death, arson, and the injuries caused by the fire, police said.