A workplace love triangle ended in death Tuesday at a Blawnox warehouse.

Sean Black and Courtney Smith, who both worked at Tri-Arc Manufacturing Co. on Blawnox’s Fountain Street, were raising three children together and had been in a romantic relationship “for several years,” police said.

But the couple separated recently, and Smith had started dating a younger Tri-Arc co-worker, Daniel Zoelle, 26, police said.

The tension came to a head Tuesday morning.

Shortly before 6:30 a.m., Black, 42, of Allegheny Township and Smith, 30, got into what police called a “domestic dispute” at their shared workplace.

The dispute turned physical. The pair started to wrestle outside Smith’s supervisor’s office.

Then, police said, Black reached for a handgun.

“Sean — No! No!” Smith yelled, according to a criminal complaint.

It was too late.

Black shot Smith four to five times in the chest, then fired two or three more shots at Zoelle, police said.

By 6:30 a.m., Allegheny County 911 had started receiving multiple calls for an active shooter at the company — a boxy, beige warehouse along the banks of the Allegheny River, near Sycamore Island.

Police from Blawnox, O’Hara and elsewhere quickly descended on the warehouse.

First responders arriving at the scene found Black kneeling on top of Smith, with two guns nearby, the complaint said.

Black surrendered, police said.

Smith was pronounced dead at the scene at 6:42 a.m., according to the Allegheny County Medical Examiner’s Office. The office did not say where she lived.

Police said that she had been shot in the back of the head.

Black was charged with homicide, attempted homicide, aggravated assault, recklessly endangering another person and two counts of carrying a firearm without a license, court records show. He was taken to the Allegheny County Jail in Pittsburgh.

Zoelle, who was shot multiple times in the torso and limbs, was taken to Allegheny General Hospital in critical condition, police said. Doctors at the North Side hospital rushed him into surgery.

Tri-Arc closed the plant Tuesday “until further notice,” spokesman Jeff Eller told TribLive.

“We are focusing on supporting our employees throughout this very difficult time,” Eller said.

Eller declined Tuesday afternoon to provide details to TribLive about any of the three employees.

Tri-Arc makes ladders, platforms, stair systems and safety gates, according to its website.

Allegheny County Police homicide detectives continue to investigate.

Anyone with information can call 833-ALL-TIPS (833-255-8477). Callers can remain anonymous.

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