Facebook user posts confession hours after his mother and friend are found dead: Authorities Casey James Lawhorn was still on the loose Sunday evening, authorities said.

A man driving on a Mississippi road phoned local police and then typed a confessional on Facebook detailing the savage double murder of his mother and a close friend, according to police.

Police say Casey James Lawhorn typed over a 1,000-word screed about how early Sunday morning he apparently was fed up with his mother and his friend and decided to kill them in his East Ridge, Tennessee, home.

As of Sunday night, Lawhorn -- who is wanted for killing his mother and his friend -- is on the lam in Jasper County, Mississippi, according to the sheriff's department there. A SWAT team surrounded his gold Taurus, but he was nowhere to be found, Tennessee authorities said.

East Ridge Police Assistant Police Chief Stan Allen told ABC News the Facebook post to be authentic, saying Lawhorn "posted a pretty specific message on Facebook detailing the crime."

According to the Facebook post from Sunday evening, Lawhorn, who in the post claims he is "almost 24," admitted to picking up a "stolen .22 LR rifle" from his bedroom and about 1:30 a.m., walked up to his friend dozing on the living room floor and "shot him in the head once."

The Facebook post said the young man "seemed to die instantly."

Then, the post suggests, he marched to his mother's dark bedroom while she was sleeping. The post claimed that his mom was inebriated when he tried pulling the trigger.

But the gun jammed, according to the post.

The post stated that he left the room momentarily to fix the weapon, and then returned. That's when he "rapidly got off two shots" in the dark.

The blood-curdling screams tested Lawhorn, according to the post.

"She started screaming the worst scream I've ever heard," according to the post. "Movies really don't do justice to how true terror sounds."

The gun jammed again, according to the post, and after fixing it a second time, Lawhorn then allegedly turned a light on and "shot at her twice more and it was over."

The post stated that Lawhorn later swiped heroin and cash from his dead friend's pockets and wallet but spared his mother's dog, Oscar.

"I didn't hurt our dog or cat, in case anyone was wondering about the animals."

Afterward, the post claims that Lawhorn was struggling with college and that he was hoping to commit suicide.

"Surely any normal person would wish death on themselves after doing what I did, seeing what I saw, and hearing what I heard," according to the post.

Allen confirmed to ABC News that dispatchers received a phone call from Mississippi -- approximately 40 miles from his home -- earlier in the evening from a man they believe to be Lawhorn tipping them off on the double homicides.

"The suspect called us and identified himself and talked to our dispatchers for some time," Allen said, noting that Lawhorn directed cops to the location of the purported double murder scene.

"He told them that he had committed the crime and that he was going to a location north of our city to find a secluded spot to kill himself," said Allen.

When officers appeared at the home, which is just south of Chattanooga, Allen said there was no answer.

"They ended up forcing entry into the home," he said.

Once inside Allen said the cops found a woman, whom they identified as Lawhorn's mother, Vi Lawhorn, and a young man whom they are not identifying. Both were dead from apparent gunshot wounds, he said.