Kisha Brown knew her ex for nearly 20 years before killing herself in Queens Monday, officials said. View Full Caption Facebook/Kisha Brown

QUEENS — Officers at a Long Island City prison are devastated after one of their own opened fire on her ex-boyfriend — also a corrections officer, whom she'd known for nearly 20 years — before turning the barrel on herself and committing suicide Monday, a union official said.

Kisha Brown, 47, who began her career at Sing Sing Correctional Facility in August 2000, chased her 44-year-old ex-boyfriend down 31st Place near the Queensboro Correctional Facility while shooting at him, missing him but striking his vehicle and another passing car with people inside, officials and witnesses said.

Her former boyfriend, who'd started working at Sing Sing about a year after Brown, managed to flee back into Queensboro unharmed before Brown fatally shot herself in the chest, officials said. She was pronounced dead at the scene.

"It broke my heart. I couldn't believe it. It stunned me. It's still breaking my heart," said Clarence Fisher, a sergeant at Sing Sing who trained both Brown and her ex when they started there.

"She was always a sweet person. This was totally unexpected," he said.

Afterwards, Queensboro correction officers could be seen out on the street hugging and consoling each other.

"They are devastated and heartbroken. It's hard to describe. It's like losing a family member," said Fisher, who is also a vice president of the Corrections officers' union.

"Some of them actually saw her. That's something they'll never forget," he added.

Investigators didn't know what sparked the shooting, an NYPD spokesman said Thursday morning. Fisher didn't recall any warning signs.

For Queensboro staff, a group of approximately 140 officers and 60 civilian staffers, Brown's suicide is particularly difficult because it's the second staff suicide in three years, according to Fisher, who spent Tuesday and Wednesday at the facility.

The Department of Corrections dispatched crisis counselors to the prison, Fisher said.

Brown and her ex were both knew each other during their time at Sing Sing, Fisher said. Her ex transferred to Arthur Kill Correctional Facility in 2004 and then Queensboro in 2006, the same year Brown also started working there, sources said.

"She was always a very good officer and so was he," Fisher said.

"As an officer, she did her job and she did it well. ... In fact, their stories in corrections kind of mirror each other because they're kind of the same. They're both good officers," the union representative added.

Brown, who lived in Queens, kept a Facebook account that documented her travels around the world to places like Jamaica, New Orleans and California.

With reporting by Trevor Kapp.