Ex-NFL star Sergio Brown was 'out of his mind' and burned all of his murdered mother's clothes before he vanished, neighbor claims

A former NFL star was 'out of his mind' in the months before his mother was found murdered in a creek, a neighbor claims.

Sergio Brown, 35, has been missing since 73-year-old Myrtle Brown's body was found washed up in Addison Creek Reservoir outside of Chicago, Illinois on Saturday. 

Brown has since uploaded a bizarre Instagram video, believed to be filmed in Mexico, where he claimed he thought his murdered mom was on vacation.

Neighbors now say they saw Brown burning his mother's clothes on a bonfire on their doorbell camera - and that family members say he 'wasn't himself' in the last few months.   

Carlos Cortez, who lives near Myrtle's home and has been assisting police with the timeline of events, told WBBM: 'They seen him taking out the trash, and they seen him have a bonfire where he burned all her clothes.'

Sergio Brown, 35, has not been located since his mother Myrtle Brown, 73, was found dead in Addison Creek Reservoir outside of Chicago, Illinois

Myrtle Brown, 73, has been remembered by neighbors as an 'outstanding woman'

Carlos Cortez, who lives near Myrtle's home, said he saw the former NFL star burning his murdered mother's clothes on a bonfire last week before he went missing

He said Sergio's behavior in the security footage was 'in line' with what family members have told him about his recent activity. 

Cortez, who said he last saw Sergio on Thursday, added: 'They said he wasn't himself the past few months. He was out of his mind.'

He remembered his neighbor Myrtle as an 'outstanding woman.' The footage showing the ex-footballer burning the clothes has not been released by police. 

The former professional athlete was last seen with his mom on August 25 as they left their home to go to a family reunion in Mississippi - but they never showed up.

After an examination of the body on Sunday, the Cook County Medical Examiner's Office ruled her death a homicide after concluding she suffered assault-related injuries. There has been no further update as of Wednesday. 

The Maywood Police Department said this is an 'active investigation' so could not share any further details at this time. 

Myrtle Brown's sister, Sheila Simmons, told WGN the last time she spoke to her sister was on Thursday, September 14.

Brown played for the Indianapolis Colts, Atlanta Falcons, Jacksonville Jaguars and the Buffalo Bills

It wasn't until around 3am Saturday morning that Simmons received the call her sister and nephew were missing. 

Simmons soon showed up at the house the two shared together and felt that things were 'out of the ordinary'.

She told WGN: 'We're going to find out what happened because it's not normal for my sister to not answer her phone, not to respond to text messages.  

'People have been reaching out to her since Friday. No one was able to reach her. 

'Now, I got the call this morning saying that she's missing, so immediately I came out here and find out my sister is dead.'

Simmons reportedly scoured the creek behind the house with police when she initially arrived, but didn't find anything.

It wasn't until later when her and other family members went back to search, they found Myrtle's dead body in the Addison Creek Reservoir.

Myrtle Brown's sister, Sheila Simmons told WGN the last time she spoke to her sister was on September 14

In a post to Facebook, Sergio's brother Nick described their mom as 'strong' and 'caring'

Nick Brown, one of Myrtle Brown’s sons and Sergio Brown’s brother, described his mom as strong, caring, diligent, fancy and funny in a Facebook post.

He said: 'It's a sad but hopeful time, and we will all get through this together. Mom always told me, “tough times don’t last” and our last conversation about tough times being temporary is my beacon of hope.

'Mom, thank you for being strong, caring, diligent, fancy, funny, and for saving my art. I won’t let you down.

'My brother Sergio is still missing. If anyone knows where he is I want him to know that I love you and please come home.'

In the clip that Sergio posted on Instagram, in which he tagged ESPN, he said: 'Fake news. It has to be the FBI, they came into my house...unwarranted. 

'They kidnapped me twice from home, the Maywood Police Department. It had to be the FBI or the Maywood Police. I thought my momma was on vacation.' 

NFL star Sergio Brown (left) and his mom, Myrtle,(right) were both reported missing on Saturday

Finishing off the incoherent ramble, Brown adds: 'That's f***ing fake news. Get the f*** out my god damn face. 

'FBI had to do it, they got the power to do some s**t . What the f**k is going on, that is fake news. Don't come f***ing with me.'

Brown had shared the video to a secondary Instagram account and not his verified profile. 

DailyMail.com has been unable to verify that the account in question belongs to Brown, who has not been named as a suspect, according to the Independent. 

In the video, Brown appears to be in a hot climate, wearing a vest and seemingly seated under a straw thatched roof, while listening to Spanish music. 

What appears to be papel picado, traditional Mexican decorative banners, can be seen strung from the ceiling above him.  

Sergio played for the University of Notre Dame before he moved on and perused his career in the NFL. He signed as undrafted free agent with the New England Patriots as a safety in 2010.

As he parted ways with the team in 2012, he then moved on and played for the Indianapolis Colts, Atlanta Falcons, Jacksonville Jaguars and the Buffalo Bills.