CHICAGO, ILLINOIS: The mystery surrounding Sergio Brown’s disappearance and his 73-year-old mother Myrtle Brown’s death is intensifying as time passes.

After Sergio’s brother, Nick Brown, reported that both the mother and son had gone missing on Saturday, September 16, the authorities retrieved Myrtle’s lifeless body from a creek near her home in the Chicago suburb Maywood, per E! Online.

According to a Maywood Police Department press release, the 73-year-old woman who celebrated her birthday on September 8, was found "unresponsive near a creek to the rear of her residence."

While the authorities are still searching for Sergio, Myrtle’s death has been investigated as a homicide as the Cook County medical examiner informed she died of "multiple injuries from an assault."

However, the news outlet CBS News revealed some further disturbing circumstances surrounding the tragedy.

Police finds footage of Sergio Brown burning his mother’s clothes

Recounting the fateful day, Myrtle’s next-door neighbor Carlos Cortez said to CBS, "The whole block was filled with family and police.”

At first, he was curious seeing the commotion in their quiet neighborhood, only to learn about how Myrtle and her 35-year-old son, Sergio Brown, had gone missing.

He said, "Her family came and knocked on the door and was looking for her cause they put out a police report because she was missing for 72 hours.”

The police later found Myrtle’s body in a creek located less than 100 yards from her home.

Cortez, who admitted seeing Myrtle and Sergio last on Thursday, September 14, said, "Myrtle, she was an outstanding woman, and I'm hoping she's in the right place and she's with God. Like I said, I never would've expected this in a million years. You only watch this on TV. And to know this happened next door, it's a tragedy.”

He further revealed to the outlet that police saw Sergio burning all of his mother’s clothes in a bonfire from Cortez’s doorbell camera.

He shared, "They seen him taking out the trash, and they seen him have a bonfire where he burned all her clothes.”

His comments about Sergio's mental balance was based on what Brown's family had told him. "They said he wasn't himself the last few months. He was out of his mind,” Cortez said.

Where is Sergio Brown now?

Sergio Brown, who started his NFL career with New England Patriots, joined teams like the Indianapolis Colts, Jacksonville Jaguars, and Buffalo Bills until his retirement in 2016.

On Saturday, September 2016, his brother Nick first posted on social media about his disappearance.

In his follow-up post on Sunday, September 17, Nick pleaded his brother to come back while informing the family’s well-wishers that Sergio was still missing.

On Saturday, September 16, the missing Sergio posted a video on his Instagram story talking about Maywood Police and the FBI, per CBS. The video has since been deleted.

However, The Neighborhood Talk posted screenshots from the bizzare video that also revealed Sergio's apparent location — Mexico City.

The same information is now being circulated online by several friends and acquaintances of Nick on Facebook. The search for Sergio Brown is still ongoing.