Updated

The desperate owner of a chimpanzee that went on a rampage in Stamford, Conn., pleaded with police over the phone to help her stop the animal from mauling her friend, telling them they had to "shoot him" when they arrived.

Police in Stamford released 911 tapes of Sandra Herold's frantic call to police Monday as her beloved 15-year-old, 200-pound chimp, Travis, was attacking 55-year-old Charla Nash.

The chimp can be heard grunting at times on the tape, as Herold cries, "He's killing my friend!"

The dispatcher says, "Who's killing your friend?"

Herold replies, "My chimpanzee! He ripped her apart! Shoot him, shoot him!"

Click here to listen to the 911 call.

Click here for photos.

After police arrive, one officer radios back: "There's a man down. He doesn't look good," he says, referring to the disfigured Nash. "We've got to get this guy out of here. He's got no face."

The chimp attacked Nash as Herold, 70, frantically stabbed her beloved pet with a butcher knife and pounded him with a shovel. Nash was in critical condition Tuesday.

She suffered "a tremendous loss of blood" from serious facial injuries, police said.

Herold said Tuesday night that Travis had nothing but love until the "freak accident."

"It's just been hell," she told MyFOXNY. "There's no way to explain it any different."

Click here to watch the MyFOXNY interview with Sandra Herold.

Police said they are looking into the possibility of criminal charges. A pet owner can be held criminally responsible if he or she knew or should have known that an animal was a danger to others.

Police said that the chimp was agitated earlier Monday and that Herold had given him the anti-anxiety drug Xanax in some tea. Police said the drug had not been prescribed for the 14-year-old chimp.

Investigators said they were also told that Travis had Lyme disease, a tick-borne illness with flu-like symptoms that can lead to arthritis and meningitis in humans. The attack was believed to be unprovoked.

"Maybe from the medications he was out of sorts," Stamford police Capt. Richard Conklin said.

Herold disputed those reports Wednesday, telling The Associated Press that she "never, ever" gave Xanax to the animal.

Nash had gone to Herold's home in Stamford on Monday to help her coax the chimp back into the house after he got out, police said. After the animal lunged at Nash when she got out of her car, Herold ran inside to call 911 and returned with a knife.

After the initial attack, Travis ran away and started roaming Herold's property until police arrived, setting up security so medics could reach the critically injured woman, Conklin said.

But the chimpanzee returned and went after several of the officers, who retreated into their cars, Conklin said. An officer shot Travis several times after the animal opened the door to his cruiser and started to get in.

The wounded chimpanzee fled into the house and retreated to his living quarters, where he died.

When he was younger, Travis starred in TV commercials for Old Navy and Coca-Cola, made an appearance on the "Maury Povich Show" and took part in a television pilot, according to a 2003 story in The Advocate newspaper of Stamford.

Herold said she was turned away from the hospital when she went to visit Nash Tuesday, MyFOXNY reported. She's trying to get Travis' body so he can be cremated on her property, but cannot due to the police investigation.

Click here to read more from MyFOXNY.com.

The Associated Press contributed to this report.