Police said Wednesday Aziz 'Bob' Yazdanpanah planted a gun on one of the victims in a Christmas Day massacre that left 7 dead in Grapevine.
Search warrants from the Christmas Day murder-suicide that left seven people dead at a Grapevine apartment reveal the gunman planted a gun on one of the victims in an attempt to make it look like he was not the only shooter.
According to search warrants released Wednesday, an officer removed a Smith and Wesson handgun from the right hand of Mohamad Hossein Zarei, one of the victims. Another officer removed a Glock from the right hand of Azizolah "Bob" Yazdanpanah, the shooter.
But forensic evidence shows that Zarei never fired a gun, Grapevine police told NBC 5. Police said Yazdanpanah planted the gun on Zarei before he turned the gun on himself.
Police said Wednesday that Yazdanpanah shot everyone and then called 911.
The Tarrant County Medical Examiner's Office said Wednesday that all of the victims were shot in the head.
The search warrants reveal more about the police response on Sunday.
Grapevine police originally said Monday they responded to the apartment in the 2500 block of Hall Johnston Road after receiving a 911 call in which no one spoke.
On Tuesday, Sgt. Robert Eberling said investigators reviewing the tape can make out a muffled cry for help in the background.
A male caller was whispering and asking for help before the call disconnected, according to the search warrants. When 911 dispatch called back, no one answered the phone, and officers were sent to the apartment complex.
Police now say Yazdanpanah made the 911 call.
No one answered the door when officers arrived at the apartment. Two officers broke down the door after looking in the windows and seeing several unresponsive people sitting on the couch and lying on the living room floor, according to the search warrants.
Dressed as Santa Claus, Yazdanpanah arrived at his estranged wife's Christmas party with two guns, executed his entire family and then killed himself, police said Tuesday.
Yazdanpanah, 56, fired the fatal shots that killed his wife, Fatemah "Nasrin" Rahmati, 55; their daughter, Nargis "Nona" Yazdanpanah, 19; and their son, Ali Yazdanpanah, 14. Rahmati's sister, Zohreh Rahmati, 58; her husband, Mohamad Hossein Zarei, 59; and their daughter, Sahra Fatemah Zarei, 22; were also killed.
The medical examiner's office said Nasrin Rahmati was shot once in the head. All of the other victims were shot multiple times. Azizolah Yazdanpanah had one gunshot wound to the head.
Investigators recovered two weapons on the scene -- a Smith and Wesson 915 model 9 mm pistol with a 15-round magazine and a Glock 23 .40-caliber pistol with a 10-round clip. According to a search warrant, one bullet was left in each gun.
At 11:16 a.m., Sahra Zarei sent a sarcastic text message to her boyfriend about Azizolah Yazdanpanah showing up to the party dressed as Santa that read: "Awesome, I guess he's trying to be father of the year."
Family friends had told NBC 5 his visit was likely unexpected.
The 911 call was made 18 minutes later. Police said Yazdanpanah made called after shooting everyone in the apartment. A muffled "help" heard in the background may have come from one of the victims, police said.
All of the victims were found in the living room with no sign of a struggle, Eberling said. Some of the victims had defensive wounds that indicate they tried to shield themselves from the bullets, he said.
Police said late Tuesday that the cause of death for all of the victims was gunshot wounds, however the Tarrant County Medical Examiner's office has not ruled on the manner of death.
Police still aren't sure of a motive and say they may never know what led to the mass shooting, the worse crime in Grapevine history.
Funeral arrangements are still pending as the families' relatives fly to North Texas from abroad and around the United States.
A memorial organized by school friends of Nona and Ali Yazdanpanah will be held at 5:30 p.m. Wednesday at Parr Park in Grapevine.
A private memorial for the entire family will be held Friday .
NBC 5's Ray Villeda and Scott Gordon contributed to this report