Gym stalker's ominous message to fitness fanatic, 25, days before she mysteriously vanished - as terrified family members reveal chilling theory

An alleged stalker sent a 25-year-old fitness fanatic an ominous message just days before she disappeared.

Doris Maricela Aguilar was reported missing on the night of July 1, when she left work and did not return to her home in Phoenix, Arizona, Fox 10 reports. 

Her car was found abandoned a week later, and a private investigator hired by her family to track her down said her cellphone has since pinged in Houston, Texas.

Family and friends now say they worry she may have been taken by her alleged stalker, a former co-worker who had sent her harassing messages.

Doris Maricela Aguilar, 25, has been missing from Phoenix, Arizona since July 1

The alleged stalker would show up in the parking lot of the gym Aguilar attended, forcing her to switch gyms three times, private investigator Steve Fischer told the station.

Just a few days before Aguilar mysteriously disappeared, on June 27, the alleged  stalker seemed to indicate he knew which facility she was now attending.

He wrote on a Facebook page with a gun as its profile picture: 'Getting my membership back... [see] you soon,' Fox 10 reports.

On June 27, just a few days before Aguilar mysteriously disappeared, an alleged stalker wrote on a Facebook page with a gun as its profile picture that he was getting his membership back - presumably to the gym that Aguilar would frequent

Aguilar had previously expressed her fear about the alleged stalker, friends and family claim.

They said that after the unidentified stalker started sending her harassing messages, Aguilar reported him to the company they worked at, and he was fired. 

But he reportedly kept re-appearing in Aguilar's life and sending her messages from the ominous Facebook account.

Besides the gun profile picture, the only other photo on the profile was of an AR-15 in the back of a car, according to Fox 10.

'I believe that guy took her,' said Aguilar's friend, David Lara.

'I really hope she is still here in Arizona and they didn't take her anywhere else.' 

Her family has revealed she had a stalker who would follow her to different gyms

Aguilar's car was eventually found abandoned on July 8 at a shopping mall near the intersection of Interstate 17 and Bethany Home Road.

The car was unlocked, with her purse and wallet inside full of cash.

Aguilar - whose friends and family describe her as a gym rat, a health nut and a hard worker - also left behind her passport and clothes, according to Univision.

She had even meal prepped for the week just one day before she went missing, her family says, noting she has no history of mental issues, drug abuse or running away.

Aguilar's mother now says that as she continues to await for any news of her daughter's whereabouts. 

'I feel like an anxious and worried mother because I need to know where my daughter is,' she pleaded in Spanish. 'I ask you all from the bottom of my heart to help me find Maricela safe and sound.' 

Aguilar's car was found abandoned at a shopping mall on July 8

Fischer says he is now requesting surveillance footage from the shopping mall where her car was found and is following up on her cell phone records.

He noted that he has also reached out to the police in Houston for assistance.

Meanwhile, police in Phoenix say they have finished processing Aguilar's car, and are awaiting the results as officers follow-up on all possible leads.