Tragic Erin Corwin – the newly pregnant 19-year-old woman killed and dumped in an abandoned mine-shaft in the California desert – was ‘super-excited’ at having a baby after suffering a miscarriage earlier this year, MailOnline can reveal.

Erin was heart-broken when she lost her first baby in February after complications during a brief pregnancy. But friends say the young girl was thrilled to fall pregnant for a second time and was looking forward to having a healthy baby.

This comes as the man accused of her murder and Erin’s alleged lover, former Marine Christopher Brandon Lee, was charged on Tuesday with killing her.

Tragic Erin Corwin – the newly pregnant 19-year-old woman killed and dumped in an abandoned mine-shaft in the California desert – was ‘super-excited’ at having a baby after suffering a miscarriage earlier this year, MailOnline can reveal

The San Bernardino District Attorney’s Office also filed the special circumstance allegation of 'lying in wait', increasing the potential penalty to life without parole or death.

'The decision regarding which penalty will be sought will be made after a full review of the facts and evidence in the case,' District Attorney Michael Ramos said.

Lee was arrested on Sunday by officers in Alaska on suspicion of murder and is currently awaiting extradition to California.

Police sources say he has admitted conducting internet searches on human body disposal, and a witness told detectives that Lee asked him 'what was the best way to dispose of a human body,' a sheriff's investigator wrote in a document filed in San Bernardino County Superior Court in support of an arrest warrant.

In addition, .22-caliber fired casings and rebar were recovered from the scene where Erin's body was found late on Saturday in an abandoned mine shaft.

The head stamp from the casings matched those on casings found in Lee's vehicle and home, the document said.

Police claim that Christopher Brandon Lee has admitted conducting internet searches on human body disposal and .22-caliber fired casings found at the murder scene match his gun

Erin’s chance of becoming a new mom was cruelly snatched away on June 28 when she vanished.

She was allegedly murdered and her killer dumped her body down a 140ft deep mineshaft in a remote area around two miles from her home on Twentynine Palms Marine Base in California. She was three-weeks pregnant.

Erin had told her Marine husband Jonathan Corwin she was headed to Joshua Tree National Park to scout trails she and her mother could later bike, but she never returned home.

Her Toyota Corolla was found two days later abandoned just blocks from the Twentynine Palms Marine Base.

According to search warrant documents, tire tracks matching those of Lee’s Jeep were found near to Erin’s car. Search and rescue teams scoured a 300-square-miles area round Joshua Tree National Park, including more than 100 mine shafts, for nearly two months before Corwin's body was found.

The investigation grew to focus on Lee, who was the Corwins' neighbor at the Marine Base, according to court papers.

Erin’s friend told investigators that Corwin and Lee were having an affair and that the unborn child might be Lee's, the papers show.

A close friend said Erin had become friends with Lee and his wife Nichole and the trio often visited a horse ranch just outside the town of Joshua Tree.

Erin Corwin, pictured with husband Jonathan, a corporal in the U.S. Marine Corps, was three weeks pregnant when she disappeared in June. He was 'super-excited' to be having a baby after a miscarriage in February

Michele Herring said she was in ‘shock’ over the murder and still can’t believe married father-of-one Lee has been charged with murder.

She told MailOnline: ‘Lee is a nice person, kind and laid back, you never saw him get angry, if anything he was the kind of guy who would step in to diffuse a situation.’

Michele said Lee and Nichole would come to the White Rock Horse Rescue Ranch at least twice a week to care for two horses they sponsored named Humorous and Mack.

She said Erin also visited with the couple and the three seemed like good friends.

‘Chris was always himself, a nice guy. I saw him hanging out with Erin but he didn’t seem flirty or give off the impression anything was going on.

‘He and Nichole were high-school sweethearts, they are very much in love and seem really close, like best friends. They have a daughter called Liberty.

‘They knew Erin from the base and she sponsored a horse called Casey so would come up to the ranch, her husband never came because he didn’t really like horses.’

Michele said Erin was 'super-excited' by her pregnancy after tragically losing a baby due to a miscarriage in February.

She said: 'She was so excited to be having a baby, she was a sweet girl, I just can't believe she's dead, who would do such a thing, they threw her away like she was a piece of garbage and to someone who was pregnant.'

Michele Herring, a close friend of Erin, Lee and his wife, said she was in 'shock' over the murder and still can't believe married father-of-one Lee has been charged with murder

Erin, together with Lee and his wife Nichole, would often visited the White Rock Horse Rescue Ranch just outside the town of Joshua Tree, California

Erin Corwin disappeared after leaving her home on the Twentynine Palms Marine Corps base on June 28. Her alleged lover Christopher Brandon Lee, 24, was arrested on Sunday in Alaska in connection with her death

Michele said Chris never showed any aggression during the year and a half she knew him.

She said he was always 'calm' and was ‘amazing’ with the rescue horses, catching the more troublesome animals with ease.

‘They all seemed to take to him, even the skittish ones,’ she said. ‘He and Nichole liked to go riding and they often volunteered helping the ranch with repairs. It was a very social thing, there is always people around the ranch.

‘I loved them both, they were part of my ranch kids, I would never in a million years have thought Chris was capable of murder.’

Lee is being held on a federal hold and will be extradited to California from Alaska where he and Nichole had moved to in July.

Authorities say Lee's wife is a 'person of interest' in the death. But Michele says the couple didn’t flee to Alaska as some reports have suggested, in fact she says they had been planning the move for several months.

‘Chris had left the military and it was always their plan to move back home in July, his last day was on July 6 and he wanted to go back to school to study,’ said Michele.

Scene: Erin Corwan's body was found at the bottom of a mine shaft several miles away from Twentynine Palms Marine Base in California where she lived. The exact location is unknown. She told her husband on the day she went missing that she was headed to Joshua Tree National Park

She said Lee and Nichole stayed at a bunk-house on the horse ranch before leaving for Alaska and it was here police carried out a search warrant.

Michele said Lee seemed ‘baffled’ when cops turned up.

Police seized a .40 caliber rifle and ammunition and a destructive device known as a potato gun. Lee was then arrested for illegally possessing the potato gun and spent two days in jail.

'Nichole was beside herself,' said friend Michele. But for another friend of Lee and Nichole the search warrant raised a few suspicions.

Former Deputy US Marshall David Lange, 68, who also visits the horse ranch, said he believed Lee knew police might search his house.

‘He hid his rifle in the main house where Isabella lives and put the spud gun in the trunk of her car,’ he told MailOnline.

‘Why would you hide those things unless you thought the police might find them. It just seemed a little odd to me.

‘Some have said that maybe he was keeping it away from his daughter but I’ve seen him up here plenty of times with his rifle, he once asked to use the bunk house so he could clean it.

'Isabella rang me after the police came round and she said she knew nothing about the rifle, Chris hadn't told her he was keeping it in her closet.'

Former Deputy US Marshall David Lange, 68, who also visits the horse ranch where Erin used to visit, said he believed Lee knew police might search his house

The murder case is being investigated by the San Bernardino County Sheriff’s Department and the investigation is ongoing.

Deputy District Attorney Sean Daugherty is prosecuting the case.

'Once again, we are faced with a terrible crime that shows absolutely no regard for the value of human life,' DA Michael Ramos said.

'Make no mistake that this office will fight to see that justice is carried out for our victim and her family.'

Authorities have so far declined to release the manner of Erin’s death.

'It is highly likely that Erin could have been harmed by an unknown firearm,' investigators wrote in the court documents.

'Sometime after Erin left with Lee, her phone was deactivated (turned off). Detectives believe if Erin was injured and left at an undisclosed location, she would not (be) able to call for help.'

Members of the Urban Search and Rescue team from San Bernardino County's Sheriff's Department prepare to recover the body of Erin Corwin from an abandoned mine shaft near Twentynine Palms, California on Sunday. Her body was found on Saturday night

Other evidence was found in the abandoned mine-shaft - one of more than 100 in the area - but San Bernardino County Sheriff John McMahon refused to disclose what that was.

Lee, a former Marine, told investigators he was not with Erin the day she went missing and had been hunting in Joshua National Park.

He told police that although the two had kissed, they had never had intercourse.

But the investigation found that Lee and Erin did have an 'intimate relationship' dating back to at least February, Sheriff's Sgt. Trevis Newport said.

Lee was honorably discharged after seven years in the Marine Corps (last serving as a rifleman in the Individual Ready Reserve) and subsequently moved his wife, Nichole, and daughter to Alaska.