Atlanta (CNN) A terrified mother tells the Snellville, Georgia, dispatcher she just heard one of her sons ask, "Where did mom go?" They're on their way upstairs now, she tells the 911 operator, barely completing her sentence before letting out a muffled scream.

The phone emits two tones as if someone is pressing the number keys. A male voice in the background says something about a phone. The mother sounds as if she's crying when she says, "The police are on their way. The police are on their way." She is no longer speaking to the dispatcher.

"Hello? ... Hello? ... Hello, ma'am?" the dispatcher calls. There is no reply, only silence on the other end.

Two Atlanta-area brothers remained behind bars Thursday and charged with multiple felonies after police said they attempted to kill their parents over the weekend.

Yvonne Ervin was treated then discharged Tuesday from Gwinnett Medical Center. Her husband, Zachary Ervin, was being released from the same facility Thursday, according to hospital spokeswoman Beth Hardy.

Chilling call for help

Police released Tuesday the audio of the call that Yvonne Ervin made Saturday morning to 911. On it, she sounds groggy and distraught as she says, "Please send someone to my house. My children are trying to kill me."

Yvonne Ervin called 911 and reported that she and husband Zachary were being attacked by their own sons.

Asked what she means, Yvonne Ervin says that 17-year-old Cameron and 22-year-old Christopher drugged her and their father's food with the anti-anxiety medication Xanax before attempting to kill them.

"That's why we were so sleepy. We didn't understand why we were so sleepy, but that's why," she says.

"How you know it was Xanax?" the dispatcher asks.

"Because that's what they said after they started attacking us. That's what they said," she says before pausing then pleading, "Please, please hurry, please."

As she speaks from her upstairs bedroom, she explains that her husband distracted Cameron and Christopher, allowing her to call 911.

"They're trying to strangle us and shoot us and they put Xanax in our food and they thought we would sleep. They tried to attack us. They beat me up. They beat him up. They're trying to kill us. Please, please, please hurry," she says, explaining that her husband was in the garage blowing a car horn in hopes of garnering the neighbors' attention.

She continues, "He was able to get away from them. He's just trying to do what he can to get attention to the house. But please, they strangled me and beat me."

The sons had their father's shotgun, she explains, and she doesn't know where her pistol is.

"Someone may have taken it, and they have his shotgun, so I don't know if they're going to plan on shooting him or not, but please, please hurry," she says.

Gwinnett County Police booking photos of brothers Cameron, 17, left, and Christopher Ervin, 22, arrested and charged with aggravated assault and arson in an alleged attack against their parents Yvonne and Zachary Ervin.

Asked a motive for her sons' behavior, she says she can't think of one. Perhaps they want insurance money, she guesses.

As the dispatcher again urges Yvonne Ervin to lock her bedroom door -- the mother had previously expressed doubt it would deter her sons -- her voice grows panicked as she hears her sons coming upstairs.

Quick thinking

Yvonne Ervin "told the 911 operator that (her husband) had distracted the sons and that she was able to call," Gwinnett County Police Sgt. Rich Long told CNN. "That was probably the lifesaving move from this event."

When police arrived at the Ervins' home in this northeast Atlanta suburb of about 19,000 people, "Zachary came out of the garage and collapsed," Long said. "He had a lot of head and body injuries from blunt force trauma and stab wounds on his back."

Cameron Ervin exited the house shortly thereafter and was detained, according to the incident report, which said that police entered the home from the garage and "immediately noticed a large amount of blood on the floor."

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Items had been thrown about the kitchen, "which was in complete disarray," the report said. Officers also discovered broken furniture throughout the house and a bloody black shotgun on a bed in the basement, it said. It was the only weapon found in the home, police told CNN.

An officer discovered Yvonne Ervin lying next to her bed and told her help was on the way, according to the report.

Yvonne Ervin "had blunt force trauma, but not as severe as the father," Long said.

Police said in their report that they found Christopher Ervin lying face down in a second-floor bathroom. He was unresponsive. Police believe he suffered injuries while struggling with his father for the shotgun, said Gwinnett County police Cpl. Deon Washington.

"I returned to Zachary Ervin and began applying pressure to his injuries," an officer wrote in the incident report. "While tending to Zachary, I asked him what occurred and he stated his son was trying to kill him. When asked, he stated he was struck in the head with a shotgun by Cameron. I attempted to gather more information, but he was having difficulty articulating what occurred because of his injuries."

'Who does that?'

Police said the sons were immediately arrested, and when an officer went to check on Cameron Ervin in the squad car, the teen told the officer, "Just kill me now," the incident report said.

"I asked him why would I want to do that," the officer wrote in the report. "He stated, 'I tried to kill my f***ing parents. Who does that?' I told him to try to relax and I would talk to him in a few."

As brutal as the attack sounds, that wasn't the full extent of it, according to police. The sons also plotted to burn the home down, and had "introduced natural gas into the house," Long said.

Christopher and Cameron Ervin have each been charged with two counts of felony aggravated assault and two felony counts of first degree arson, according to Long.

Under Georgia state law, 17-year-olds are considered adults in criminal cases, so both will be tried as adults, Long said.

"There is no official motive at this point, but there has to be something more to this. I'm sure they didn't just wake up and decide to kill their parents yesterday," Long said on Sunday.

The brothers were to be appointed defense attorneys Sunday, but it was not immediately clear if that had happened or who the attorneys are, CNN affiliate WSB reported. Both suspects are expected to be in court at some point this week, Long said.