Just before 3 a.m. Sunday, a silver Dodge Stratus and a green Chevrolet Silverado pulled into the parking lot of a self-serve carwash in western Pennsylvania.From the Dodge sedan, two people - 27-year-old William Scott Porterfield and 25-year-old Chelsie Lou Cline - stepped out into the chilly night air and walked to the side of the business.There, they were gunned down, police said.Those in the Silverado wouldn't even make it out of their truck. The driver and a front-seat passenger - 23-year-old Courtney Sue Snyder and 21-year-old Seth William Cline - were shot and killed inside the parked vehicle.Another passenger, a woman sitting in the back seat of the truck, scrambled to take cover as bullets shattered glass around her.The suspect, 28-year-old Timothy O'Brien Smith, was later found at the carwash armed and wearing body armor - and bleeding from a gunshot wound to his head so severe, police said, that he wasn't expected to survive.Smithwas initially placed on life support, then pronounced dead at a hospital just before 10 p.m. Sunday, police said.Policesaid they discovered a grisly scene Sunday morning after responding to reports of overnight gunfire at Ed's Car Wash in Melcroft, Pa. The mass shooting, which left four victims dead and one injured,stunned residents in the "fairly quiet" unincorporated communityabout 50 miles southeast of Pittsburgh.As of late Sunday, authorities said they hadn't determined a motive for the shootings. But relatives of the victims, speaking to local reporters, said the suspected gunmanwas motivated by jealousy after a brief relationship with Chelsie Cline.Sierra Kolarik, 24, whoidentified herself as Chelsie Cline's half sister, told WPXI Newson Sunday that Smith and Cline had dated briefly but broken up months ago. Nevertheless, he continued to pursueher, Kolarik said."He would leave her stuff on her car," Kolarik told the news station. "She'd get done with work, and she'd come out and there would be a case of beer on her hood or scratch-off tickets or anything. If he found out she was sick, he'd bring her flowers."After the shooting, some wondered whether they had missed any signs leading up to the violence.According to an image published bythe Pittsburgh Tribune-Review, Chelsie Cline shared a Facebook post four days before the shooting that read: "After this week I rlly need to get taken out .â.â. on a date or by a sniper either one is fine w me at this point." The first and only reply was reportedly from Smith's account: "I could do both," he wrote, according to the newspaper.By Monday, several other people hadcommented on the post, wondering why Smith's reply wasn't taken seriously."[Smith] came off as the most kindhearted person" but had become obsessed with Cline, Kolarik told the Tribune-Review. When asked about Smith's interests, Kolarik replied: "Guns and guns and guns and shooting and beer and rolling cigarettes."Police would not say whether victims Chelsie Cline and Seth William Cline were related.Jenna Porterfield, 24, who identified herself as the wife of victim William Scott Porterfield,told the Pittsburgh Post-Gazettethey had gotten married in November but were having marital problems. She is pregnant with his child, she added.When police asked about possible infidelity, Jenna Porterfield responded that her husband had spent the previous two days with Chelsie Cline, according to the Post-Gazette."I'm not holding that against Will. We weren't fighting. We were fixing," Porterfield told the newspaper. "And if he was with someone else while we were having problems, honestly, I don't care what he did. I'm not going to hold that against him.I'd give anything to have him back."Early Sunday, police reported five people dead before correcting the number to four and naming the suspect as one of the injured. Police have not identified the female passenger who survived the shooting - only stating that she is in her early 20s - but they said she suffered minor injuries from breaking glass."Obviously, it's a traumatic experience for her," Sgt. Jeremy Barni, a supervisor with the Pennsylvania State Police, said at a news conference Sunday. "We believe she was able to hide, duck downward."Smith was armed with an AR-15 semiautomatic rifle, a 9mm handgun and a .308 rifle, police said, and was wearing a body armor carrier without the ballistic panels inserted. The four victims were pronounced dead at the scene and had been shot with an AR-15 semiautomatic rifle and a 9mm handgun, police said.Police did not say Sunday whether Smith owned the weapons legally.He was initially placed on life support Sunday, WPXI News reported."It is a possibility the gunshot wound to Smith was self-inflicted," Fayette County District Attorney Richard Bower said at a news conference Sunday. "However, that determination has not been made at this time."Bower said police believe that Smith arrived at Ed's Car Wash ahead of the others and parked his red Toyota Tacoma on the side of the two-bay carwash where Porterfield and Chelsie Cline were later shot and killed.It was unclear whythe victimsdrove to the carwash in the middle of the night. Authorities said Sunday they were continuing to go through video surveillance footage and cellphone messages as part of the investigation.A Pennsylvania State Police spokesman said Saturday that there was no indication of drug activity.Shari Bukovac, who owns the carwash with her husband, Ed, told The Washington Post on Sunday that, although the self-serve carwash is open 24 hours a day, no employees wereon the property when the shooting took place.A neighbor called them in the middle of the night to inform them of the shooting, Bukovac said, adding that they still didn't know much more than what was being reported on television.Bukovac characterized Melcroft as "fairly quiet" and said nothing of this magnitude has happened at the carwash in the roughly two decades they've owned it."I guess at night there's been some people hanging out there," she said. "We've been broken into a time or two. But otherwise, people arejust hanging out down there, I guess."This post has been updated.Read more:Two students dead, 12 other people wounded in Kentucky high school shootingOne student wounded, 16-year-old boy in custody after school cafeteria shooting in TexasLas Vegas police say they have not found a motive for shooting rampage