Police say the suspect, 66-year-old Jose Everaldo Reyes, frequently biked around the victim's Bronx construction site and brought sandwiches to 52-year-old Lizbeth Mass.
But on Wednesday, after the two had a brief discussion, police say Reyes left, returned with a stolen .44 caliber Smith and Wesson, and shot Mass six times.
He remains hospitalized after Mass' boyfriend, who was visiting her at lunchtime, ran Reyes down with his car and held him until police arrived.
A memorial now sits at the scene.
"As we can discern at this time, she is a friendly person," NYPD Chief of Detectives James Essig said. "We don't know what triggered him in that, but there was no relationship to those two..."He comes by on his bike frequently. She always has a friendly smile for him, talks to him."
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The boyfriend is not being charged at this time, but the investigation is active and ongoing.
"We are deeply saddened by the tragic loss of our employee Lizbeth Mass," Northeast Remsco Construction, Inc., said in a statement. "Liz was a mother, grandmother, sister, daughter, co-worker, and beloved member of the New York construction community. She will be remembered for her kindness and professionalism. The Northeast Remsco family extends our heartfelt condolences to her family and express our deep appreciation for her service to our company and the city of New York."
Detectives said Thursday that the gun was owned by a retired NYPD officer and that Reyes stole it while doing work at his house.
When the owner saw the shooting story on the news, he checked on his gun and realized it was missing.
The NYPD will now investigate that, and the department also confiscated two other personal weapons from him as a routine part of the investigation.
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Area residents said Mass had been at the construction site for a couple of weeks and was known to be animated while holding a sign telling people to slow down.
"We've come to know her," said one man who didn't want to be identified. "She's here every day, she's waving flags, she's very animated, she has a very bubbly personality, even the people that go for their morning walks have come to know her."
The man told Eyewitness News that a colleague was nearby when the shooting happened.
"This guy used to bring her sandwiches every day," the man said. "Today, he brought bullets instead."
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