The unhinged gunman who killed three Pennsylvania cops from the same police department was identified by sources Thursday as a 24-year-old man who was wanted for allegedly stalking his ex-girlfriend while brandishing an AR-15.

Matthew James Ruth, of Hanover, allegedly unleashed the fatal round of gunfire that also wounded two officers on Wednesday as police were following up on a domestic-related probe that began the day before, a law enforcement official told The Associated Press.

Ruth, who was killed by police during the chaotic scene, landed on law enforcement’s radar the night before when he was suspected of lurking around a home in North Codorus Township late Tuesday night, according to a probable cause affidavit obtained by local news outlets.

He was decked out in camouflage, looking into the home with binoculars, a 911 caller said — with trail cam images showing an AR-15 rifle around his chest and peering into the home, according to the affidavit.

The caller’s daughter told Northern York County Regional Police Department cops that she and Ruth only dated for a brief time, and he was never invited over to her house, according to the court docs.

While Ruth’s black pickup truck was found by responding officers, authorities couldn’t track down the suspect after hours of searching.

Ruth was charged earlier Wednesday with stalking, prowling at nighttime, and criminal trespass, according to court records.

Police returned to the same North Codorus house Wednesday afternoon as part of their investigation, but all hell broke loose as they took on heavy fire around 2:10 p.m., police said.

Ruth is accused of ambushing police with one neighbor telling WGAL he heard at least 30 gunshots. 

The three slain officers have not been identified, but all belonged to the Northern York County Regional Police Department.

A fourth surviving officer also belonged to the same department. That cop and another officer from a different agency are listed in critical, but stable condition, authorities said. An update on the surviving officers was not offered Thursday, but a news conference is scheduled for 3 p.m.

“Yesterday was a dark and heartbreaking day for the Northern York County Regional Police Department and for all of York County,” the department said in a statement.

The ex-girlfriend also reported to police on Sept. 11 about an Aug. 20 incident in which her pickup truck was lit on fire in her driveway, and while she thought it might be Ruth, she wasn’t sure, according to a police report obtained by Fox 43.

“This kind of violence isn’t OK. We need to do better as a society,” said Gov. Josh Shapiro of the shooting. 

“We need to help the people who think picking up a gun, picking up a weapon is the answer to resolving disputes … So we don’t need to deal with tragedies like this.”