Ballistics tests confirm that the gun used in the murder-suicide was the weapon that killed Givens, Debbie Tanna, a spokeswoman with the Cumberland (N.C.) Sheriff's Office, said Wednesday.
Tanna declined to say what type of handgun was used. Authorities with the Camden County Prosecutor's Office said they recovered a Sig Sauer .357 handgun from Navek's vehicle and at least 11 rounds of ammunition.
Authorities suspected that Navek killed Givens after her body was found, but on Wednesday, Tanna did not explicitly link him to her death.
One former colleague on Wednesday described Navek as being abrasive with coworkers during his time at Virtua.
He had "multiple problems" with nurses and others and had argued with Houshmandpour at one point, the former colleague, who asked to be quoted anonymously, said in an interview.
"He wasn't easy to deal with. If he was told to do certain things, he would argue about them. He wouldn't take input from other people," the former colleague said.
"He definitely had some anger issues. If he was confronted about something that went wrong, he would usually snap, and then he would try to find an excuse to get out of it and blame it on other people."
Navek had blamed Houshmandpour for his dismissal a year and a half ago from Virtua's residency program, his ex-fiancee's mother, Forogh Mozaffari, told the Associated Press.
Virtua has declined to say why Navek was no longer with the program.
Houshmandpour, 32, was just a couple of months away from concluding his own residency at Virtua.
Last week, a friend of Givens from Fayetteville told the Daily News that Navek made her uneasy.
Kris Delgado, a Fayetteville bar owner, said she had warned Givens that Navek seemed erratic and unstable, and drank a lot.
"All the signs were there. All her friends warned her. He wasn't right in the head," Delgado told the Daily News. "She knew it."
According to her obituary in the Fayetteville Observer, Givens is survived by her parents, husband, three children, and a grandson, among others.
She had been dating Navek, a Philadelphia native, for four to five months. The two had met at the Womack Army Medical Center, where Navek, a captain in the Army Reserve, had been assigned as physician since September in the acute minor illness clinic.
Navek split his time between Fort Bragg and Williamstown, where he had lived with his fiancee, Shohreh Sameni, before she recently moved out with their toddler son.
Sameni, also a Virtua resident, broke up with Navek after she found out about his relationship with Givens, Sameni's mother told the Associated Press.
Neither she nor her mother could be reached for comment Wednesday.
During the Easter holiday, Givens and Navek visited his family in Philadelphia, authorities said. They left for North Carolina on April 8.
Two days later, Navek returned to Philadelphia. He dropped his Mercedes off at his family's home in Philadelphia and borrowed a family member's Nissan.
He then drove to Voorhees, where he fatally shot Houshmandpour several times as he left for work.
Navek's family in South Philadelphia could not be reached Wednesday.
Navek worked as a paramedic for four years, a city spokesman said. He later earned a medical degree from St. George's University in Grenada, said the former colleague.
Houshmandpour was an Iranian native and a married father of a 20-month-old daughter.
After completing his residency, he was contemplating relocating either to South Carolina, where he had a job offer, or Boston, where his wife had been recently accepted in a Harvard University postgraduate program.
"He was a man you could trust. He was a wonderful dad, a wonderful husband. He was a great friend," said Simon S. Boulattouf, a former Virtua resident who now practices medicine in Glen Burnie, Md.
Boulattouf added: "He was never the guy you would expect somebody to go out and kill. His loss is going to affect everyone's life. Everyone is going miss him."
Contact Darran Simon
at 856-779-3829 or firstname.lastname@example.org, or follow on Twitter @darransimon.
Daily News staff writer Jason Nark contributed to this article.