A Cape Verdean woman who walked in on her handcuffed sister allegedly being raped by a twisted mama’s boy was shot to death and her sister riddled with bullets as they ran for help in a Brockton bloodbath sources said may have been fueled by racial hatred.

An elderly homeless man who may have witnessed the carnage in the middle of Clinton Street was also gunned down, while two hero Brockton cops who captured the rampaging gunman cheated death by inches.

If the shell-littered crime scene wasn’t horrific enough, sources told the Herald that the suspect, Keith Luke, 22, had “hundreds” of rounds of ammunition in his van and may have been plotting to massacre blacks and Jews.

Luke, a former neighbor of the Cape Verdean sisters at 103 Clinton St., is scheduled to be arraigned today in Brockton District Court on two murder charges, as well as armed assault with intent to murder, aggravated rape and kidnapping.

Sources described him as an overweight man who still lived with his mother.

Jose Canuto, 30, who lives across the street from the sisters, said the surviving sibling still had handcuffs dangling from one wrist when he ran outside to assist them after hearing gunshots.

“I looked outside and saw one of the girls running, blood all over her,” Canuto said, his voice barely above a distressed whisper. “I grabbed her and sat her down and told her to hang on while I ran to her sister, who I could see a distance away. But I could see her sister was already dead.”

Canuto said it was clear to him the surviving sister - who was in critical condition last night - had been shot in the chest. Though in shock, he said she kept repeating, “The guy on the second floor, the guy on the second floor.

“She was saying she was shot in the head,” said Canuto, “but there was so much blood. I tried my best. I really tried. I thought if I couldn’t save one, maybe I could save the other.”

Authorities said the second murder victim was in his 60s. Neighbors said he was well-known to them as a homeless man who often came down Clinton Street in search of discarded cans.

A relative of the sisters said the girl who died was 19 and the survivor was 21. “They’ve only been here for a year,” said the woman. “I have no idea why anyone would target them.”

The events began unfolding with a report of shots fired at 103 Clinton St. just after 12:45 p.m. yesterday. Police Chief William Conlon praised the two officers who came under fire trying to stop the suspect from fleeing in his van.

“Officer Bill Devine was further ahead (of the chase). He knew the suspect was heading his way. As (Luke) approached Officer Devine, (Luke) reached out of his window and fired a shot at him. The bullet missed Officer Devine and went through his windshield,” he said.

Officer Jim Cronshaw, monitoring his radio while on a lunch break, jumped into the action to divert traffic away from Luke. Luke allegedly fired at him, too, and Cronshaw fired back, causing Luke to crash his van into three other vehicles at North Quincy and Court streets.

“If it were not for the actions of the officers, we could have been looking at something much worse that what happened,” Conlon said. “They really put themselves out there.”