The shooting was the result of a domestic dispute, according to local media.
Twenty-seven-year-old William Porterfield, 25-year-old Chelsie Cline, 23-year-old Courtney Snyder and 21-year-old Seth Cline were all killed. The gunshot wound appeared to be self-inflicted, authorities said.
Cline's relative, Sierra Kolarik, told the Pittsburgh Tribune-Review that Smith had moved toward becoming focused with the woman.
Melcroft located nearly 55 miles (89 kms) southeast of Pittsburgh.
One person was shot in Stowe Township Sunday afternoon. The police have said there is no immediate threat to the public as of now.
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Family members and friends console each other after four people are killed at a Pennsylvania vehicle wash.
But state police say they haven't yet confirmed that or a motive for the shootings that occurred early Sunday in the Melcroft community of Saltlick Township, about 55 miles (89 kilometers) southeast of Pittsburgh.
WPXI-TV reported that Smith shot the victims with a semi-automatic rifle and a handgun.
Four of those victims died at the scene, and the fifth died later at a hospital, a police spokesman told the Pittsburgh Post-Gazette. The condition of the injured person is not clear. She also said she knew that "her husband had spent the past two days with Chelsie Cline who had ended her relationship with Smith a couple of days earlier".
A man who lives nearby told the newspaper that he heard about 30 gunshots over a span of several minutes.
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She uncovered that Cline had gone through the end of the week with her killed spouse of three months as both of them battled through a conjugal unpleasant fix.
WTAE reported that it happened at a self-serve auto wash in Melcroft shortly before 3 a.m. Four of the victims were pronounced dead at the scene, while another died at a hospital.
Smith was first to arrive at the scene and was parked on the side of the two-bay auto wash when Porterfield and Cline arrived, police said.
She characterized Melcroft, an unincorporated community in Western Pennsylvania's Fayette County, as "fairly quiet" and said that nothing of this magnitude had ever happened at the auto wash in the roughly two decades the couple hax owned it.
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